Mr. Justice Rehnquist
delivered the opinion of the Court.
Petitioners are the owners and managing agents of two ships which are registered under the laws of Liberia and fly the Liberian flag. They sought injunctive relief in the state courts in Texas to bar picketing of their vessels by respondent unions. The trial court denied relief, finding that the dispute was “arguably” within the jurisdiction of the National Labor Relations Board and that the jurisdiction of the state courts was therefore pre-empted. The Texas Court of Civil Appeals affirmed, and we granted certiorari, 412 U. S. 927 (1973), to consider whether the activities here complained of were activities “affecting commerce” within the meaning of §§ 2 (6) and (7) of the National Labor Relations Act, 49 Stat. 450, 29 U. S. C. §§ 152 (6) and (7). We hold that they were not, and therefore reverse the judgment of the Court of Civil Appeals.
I
The vessels Northwind and Theomana are ships of Liberian registry, carrying cargo between foreign ports and the United States. Northwind is owned by petitioner Westwind Africa Line, Ltd., a Liberian corporation, while Theomana is owned by petitioner SPS Bulkcarriers Corp., a Liberian corporation, and managed by petitioner Windward Shipping (London) Ltd., a British corporation. The crews of both vessels are composed entirely of foreign nationals, represented by foreign unions and employed under foreign articles of agreement.
Respondents are American maritime unions, apparently representing a substantial majority of American merchant seamen. Alarmed by an accelerating decline in the number of jobs available to their members, these unions agreed to undertake collective action against foreign vessels, which they saw as the major cause of their business recession. Specifically, these unions agreed to picket foreign ships, calling attention to the competitive advantage enjoyed by such vessels because of a difference between foreign and domestic seamen’s wages. All parties concede that such a difference does exist.
The picketing here occurred at the Port of Houston, Texas, in October 1971. Both Northwind and Theomana were docked within the port, and respondents established picket lines in front of each vessel. There were four pickets assigned to each vessel, carrying signs which read:
“ATTENTION TO THE PUBLIC THE WAGES AND BENEFITS PAID SEAMEN ABOARD THE VESSEL THEOMANA [NORTH-WIND] ARE SUBSTANDARD TO THOSE OF AMERICAN SEAMEN. THIS RESULTS IN EXTREME DAMAGE TO OUR WAGE STANDARDS AND LOSS OF OUR JOBS. PLEASE DO NOT PATRONIZE THIS VESSEL. HELP THE AMERICAN SEAMEN. WE HAVE NO DISPUTE WITH ANY OTHER VESSEL ON THIS SITE.”
[Printed names of the six unions.]
These signs were supplemented by pamphlets of similar import. The pickets were instructed not to discuss the picketing with anyone, and they appear to have followed their instructions.
The picketing, although neither obstructive nor violent, was not without effect. Longshoremen and other port workers refused to cross the picket lines to load and unload petitioners’ vessels. Petitioners filed separate suits in a Texas state court, asking the court to enjoin the picketing as tortious under Texas law. The primary basis for petitioners’ claim was that the picketing sought to induce the owners and crews to break pre-existing contracts. Respondents presented several defenses, contending in particular that the jurisdiction of the Texas court was pre-empted by the National Labor Relations Act.
The trial court sustained this contention, holding that jurisdiction properly lay with the NLRB, and the Texas Court of Civil Appeals affirmed. That court found that state jurisdiction was pre-empted by the Act when “the activities complained of are arguably either protected by section 7 or prohibited by section 8 of the NLRA as amended by the LMRA,” see San Diego Building Trades Council v. Garmon, 359 U. S. 236 (1959), and that the conduct here met that test. The court rejected petitioners’ argument that the picketing interfered with the “maritime operations of foreign-flag ships,” see McCulloch v. Sociedad Nacional, 372 U. S. 10 (1963), in such manner as to remove it from the Board’s jurisdiction. The court concluded:
“If [the picketing] but voices a complaint as to foreign wages and urges the public not to patronize foreign vessels it does not engage in matters outside of commerce. It is peaceful picketing, publicizing a labor dispute, of such a character that its validity is suggested by the Court’s holding in the Marine Cooks case, supra. It is, at least arguably, a protected activity under section 7 of the LMRA. As such, it is an activity as to which the exclusive jurisdiction to determine its propriety has been preempted to the NLRB.”
Petitioners contend that the Court of Appeals too narrowly construed this Court’s decisions denying the NLRB jurisdiction in cases involving foreign-flag ships. We therefore begin by examining the principles established by those decisions for determining the jurisdiction of the NLRB.
II
In a series of cases decided over the past 17 years, this Court has discussed the application of the Labor Management Relations Act in situations which might be broadly described as disputes between unions representing workers in this country and owners of foreign-flag vessels operating in international maritime commerce. Benz v. Compania Naviera Hidalgo, 353 U. S. 138 (1957), is the leading case on the subject. In Benz the question was whether the Labor Management Relations Act, 1947, precluded a diversity suit for damages brought in the United States District Court by foreign shipowners against picketing American unions. The picketing had been undertaken in Portland, Oregon, to support striking foreign crews employed under foreign articles and had resulted in the refusal of workers to load and repair the docked foreign ships. The District Court had awarded damages and the Court of Appeals affirmed.
This Court held that the shipowners’ action was not pre-empted by the Labor Management Relations Act. Studying the legislative history of the Act, the Court found no indication that it was intended to govern disputes between foreign shipowners and foreign crews. On the contrary, the Court concluded that the most revealing legislative history strongly suggested the bill was a “bill of rights ... for American workingmen and for their employers.” Id., at 144. (Emphasis in original.) The Court stated that this history “inescapably describes the boundaries of the Act as including only the workingmen of our own country and its possessions.” Ibid.
Recognition of the clear congressional purpose to apply the LMRA only to American workers and employers was doubtless a sufficient reason to place the picketing in Benz outside the Act. But the Court in that case made clear its reluctance to intrude domestic labor law willy-nilly into the complex of considerations affecting foreign trade, absent a clear congressional mandate to do so:
“For us to run interference in such a delicate field of international relations there must be present the affirmative intention of the Congress clearly expressed. It alone has the facilities necessary to make fairly such an important policy decision where the possibilities of international discord are so evident, and retaliative action so certain.” Id., at 147.
In the 17 years since Benz was decided, Congress has in no way indicated any such “affirmative intention,” and this Court has continued to construe the LMRA in accordance with the dictates of that case.
The reasoning of Benz was reaffirmed in McCulloch v. Sociedad Nacional, 372 U. S. 10 (1963), and Incres S. S. Co. v. Maritime Workers, 372 U. S. 24 (1963), decided together six years later. In McCulloch, we held that the National Labor Relations Board had improperly assumed jurisdiction under the Act to order an election involving foreign crews of foreign-flag ships. Rejecting the Board’s “balancing of contacts” theory, the Court said:
“[T]o follow such a suggested procedure to the ultimate might require that the Board inquire into the internal discipline and order of all foreign vessels calling at American ports.” 372 U. S., at 19.
In lucres we applied this rationale to a situation involving union picketing of a foreign ship in an effort to organize the foreign crew. Reversing the holding, of a New York state court that the picketing was arguably within the jurisdiction of the NLRB, the Court said:
“The Board’s jurisdiction to prevent unfair labor practices, like its jurisdiction to direct elections, is based upon circumstances 'affecting commerce,’ and we have concluded that maritime operations of foreign-flag ships employing alien seamen are not in ‘commerce’ within the meaning of § 2 (6), 29 U. S. C. § 152 (6).” 372 U. S., at 27.
But Benz and its successor cases have not been read to exempt all organizational activities from the Act’s protections merely because those activities in some way were directed at an employer who was the owner of a foreign-flag vessel docked in an American port. In Longshoremen v. Ariadne Co., 397 U. S. 195 (1970), the Court held that the picketing of foreign ships to protest substandard wages paid by their owners to nonunion American longshoremen was “in ‘commerce’ within the meaning of § 2 (6), and thus might have been subject to the regulatory power of the National Labor Relations Board.” Id., at 200. The pickets in Ariadne, unlike the pickets in Benz or Inores, were primarily engaged in a dispute as to whether an employer should hire unionized or nonunionized American workers to perform longshoremen’s work, and the substandard wages which they were protesting were being paid to fellow American workers. The Court specifically noted: “[T]his dispute centered on the wages to be paid American residents.” Id., at 199.
The term “in commerce,” as used in the LMRA, is obviously not self-defining, and certainly the activities in Benz, McCulloch, and Inores, held not covered by the Act, were literally just as much “in commerce” as were the activities held covered in Ariadne. Those cases which deny jurisdiction to the NLRB recognize that Congress, when it used the words “in commerce” in the LMRA, simply did not intend that Act to erase longstanding principles of comity and accommodation in international maritime trade. In Lauritzen v. Larsen, 345 U. S. 571, 577 (1953), the Court commented on the congressional intent with respect to the Jones Act of 1920 in these words:
“But Congress in 1920 wrote these all-comprehending words, not on a clean slate, but as a postscript to a long series of enactments governing shipping. All were enacted with regard to a seasoned body of maritime law developed by the experience of American courts long accustomed to dealing with admiralty problems in reconciling our own with foreign interests and in accommodating the reach of our own laws to those of other maritime nations.”
We are even more reluctant to attribute to Congress an intention to disrupt this comprehensive body of law by construction of an Act unrelated to maritime commerce and directed solely at American labor relations.
Ill
The picketing activities in this case do not involve the inescapable intrusion into the affairs of foreign ships that was present in Benz and lucres; respondents seek neither to organize the foreign crews for purpose of representation nor to support foreign crews in their own wage dispute with a foreign shipowner. But those cases do not purport to fully delineate the threshold of interference with the maritime operations of foreign vessels which makes the LMRA inapplicable.
The picket signs utilized at the docks where the Northwind and Theomana were tied up protested the wages paid to foreign seamen who were employed by foreign shipowners under contracts made outside the United States. At the very least, the pickets must have hoped to exert sufficient pressure so that foreign vessels would be forced to raise their operating costs to levels comparable to those of American shippers, either because of lost cargo resulting from the longshoremen’s refusal to load or unload the vessels, or because of wage increases awarded as a virtual self-imposed tariff to regain entry to American ports. Such a large-scale increase in operating costs would have more than a negligible impact on the “maritime operations” of these foreign ships, and the effect would be by no means limited to costs incurred while in American ports. Unlike Ariadne, the protest here could not be accommodated by a wage decision on the part of the shipowners which would affect only wages paid within this country.
In this situation, the foreign vessels’ lot is not a happy one. A decision by the foreign owners to raise foreign seamen’s wages to a level mollifying the American pickets would have the most significant and far-reaching effect on the maritime operations of these ships throughout the world. A decision to boycott American ports in order to avoid the difficulties induced by the picketing would be detrimental not only to the private balance sheets of the foreign shipowners but to the citizenry of a country as dependent on goods carried in foreign bottoms as is ours. Retaliatory action against American vessels in foreign ports might likewise be considered, but the employment of such tactics would probably exacerbate and broaden the present dispute. Virtually none of the predictable responses of a foreign shipowner to picketing of this type, therefore, would be limited to the sort of wage-cost decision benefiting American workingmen which the LMRA was designed to regulate. This case, therefore, falls under Benz rather than under Ariadne.
Since we hold that respondents’ picketing was not “in commerce” as defined by the Act, we do not reach the question of whether the activity was otherwise of such a nature that state courts would be precluded by the LMRA from entertaining an action to enjoin it. Our conclusion that the activities here involved were not “in commerce” within the meaning of §§ 2 (6) and (7) of the NLRA, as amended by the LMRA, resolves a question which, of course, is one for the courts in the first instance. Ariadne, 397 U. S., at 200. The Court of Civil Appeals was therefore wrong in holding that the courts of the State of Texas were prevented by the LMRA from entertaining petitioners’ suit for an injunction.
Reversed.
482 S. W. 2d 675 (1972).
The definitions in §§ 2 (6) and (7), 29 U. S. C. §§ 152 (6) and (7), as amended by the Labor Management Relations Act, 1947, are as follows:
"(6) The term ‘commerce’ means trade, traffic, commerce, transportation, or communication among the several States, or between the District of Columbia or any Territory of the United States and any State or other Territory, or between any foreign country and any State, Territory, or the District of Columbia, or within the District of Columbia or any Territory, or between points in the same State but through any other State or any Territory or the District of Columbia or any foreign country.
“(7) The term ‘affecting commerce’ means in commerce, or burdening or obstructing commerce or the free flow of commerce, or having led or tending to lead to a labor dispute burdening or obstructing commerce or the free flow of commerce.”
Respondents describe themselves in their brief as “six labor organizations who collectively represent the overwhelming majority and practically almost all American merchant seamen.” Brief for Respondents 2.
The petitioners state:
“We do not contest the fact that the wages of foreign crews on foreign ships are substantially lower than those paid to American seamen on American ships.” Brief for Petitioners 19.
The brief notes some estimates that the American wage costs are between 2% to 4 times higher than the foreign wage costs. Id., at 19 n.
These pamphlets stated:
“To the Public — American Seamen have lost approximately 50% of their jobs in the past few years to foreign flag ships employing seamen at a fraction of the wages of American Seamen.
“American dollars flowing to these foreign ship owners operating ships at wages and benefits substandard to American Seamen, are hurting our balance of payments in addition to hurting our economy by the loss of jobs.
“A strong American Merchant Marine is essential to our national defense. The fewer American flag ships there are, the weaker our position will be in a period of national emergency.
“PLEASE PATRONIZE AMERICAN FLAG VESSELS, SAVE OUR JOBS, HELP OUR ECONOMY AND SUPPORT OUR NATIONAL DEFENSE BY HELPING TO CREATE A STRONG AMERICAN MERCHANT MARINE.
“Our dispute is limited to the vessel picketed at this site, the S. S.” (App. 21).
The courts below considered only this ground advanced by respondents, finding it dispositive. We express no opinion on the merits of respondents’ other contentions.
482 S. W. 2d, at 678.
Id., at 680-682.
Id., at 682.
Benz v. Compania Naviera Hidalgo, 353 U. S. 138 (1957); McCulloch v. Sociedad Nacional, 372 U. S. 10 (1963); Incres S. S. Co. v. Maritime Workers, 372 U. S. 24 (1963); Longshoremen v. Ariadne Co., 397 U. S. 195 (1970).
The Court in McCulloch also noted that the Board’s actions had “aroused vigorous protests from foreign governments and created international problems for our Government.” 372 U. S., at 17.
The evidence in Ariadne showed that the work at issue was performed partly by members of the foreign ships’ crews and partly by outside labor. 397 U. S., at 196. Those workers included in the classification “outside labor” were nonunion members. This Court noted that “[t]he participation of some crew members in the longshore work does not obscure the fact that this dispute centered on the wages to be paid American residents, who were employed by each foreign ship not to serve as members of its crew but rather to do casual longshore work.” Id., at 199.
The basic question at issue in Lauritzen was whether American or Danish law applied to a maritime tort which occurred in Havana Harbor. Although analysis of the Jones Act there obviously involved different considerations from analysis of the Labor Management Relations Act here, it is interesting to note that some arguments at least are common to both cases. In Lauritzen this Court rejected a “candid and brash appeal” made by the seamen and various amici that the Court should “extend the law to this situation as a means of benefiting seamen and enhancing the costs of foreign ship operation for the competitive advantage of our own.” 345 U. S., at 593. We observed at that time that such arguments were obviously better directed to Congress.
We do not find the rationale of Marine Cooks & Stewards v. Panama S. S. Co., 362 U. S. 365 (1960), to be applicable here. Although that case involved a labor situation strikingly similar to the situation involved in this case, the controlling question in Marine Cooks was the jurisdiction of a federal district court to enjoin picketing of a foreign-flag ship under the Norris-LaGuardia Act, 29 U. S. C. § 101 et seq. The Court held that in such circumstances the district courts had no jurisdiction. However, as we later noted in McCulloch, 372 U. S., at 18, Marine Cooks “cannot be regarded as limiting the earlier Benz holding . . . since no question as to ‘whether the picketing . . . was tortious under state or federal law' was either presented or decided.” Obviously the question whether Congress intended the federal courts to stay out of the labor injunction business involves significantly different considerations from the question whether Congress intended the Labor Management Relations Act to apply to the type of picketing of foreign ships involved here.