The expression "national security" or its close similes lacks a precise meaning, even in the public policy literature. Nevertheless, the concept appears in over 30 federal statutes. In most instances, the term is undefined, an important oversight in light of the significant powers these statutes accord the government. Under these circumstances, how courts review government invocations of "national security" is of real importance. With some exceptions, courts applying s. 7 of the Charter and standard administrative law doctrines have accorded substantial deference to government national security determinations. When largely deferential substantive review of the ambiguous concept of national security is coupled with the ex parti and in camera context in which these cases are often heard, the net effect is to leave government with a freer hand in national security matters than in other domains of administrative decision making. Several possible responses to this problem are proposed.