time citing Sunnen for the proposition that a change in the governing legal principles can prevent the application of issue preclusion). Thus, we conclude that this Precision Air Parts statement is not good law with respect to issue preclusion. 5 . The TIA states, "[t]he district courts shall not enjoin, suspend or restrain the assessment, levy or collection of any tax under State law where a plain, speedy and efficient remedy may be had in the courts of such State.” 28 U.S.C. § 1341. 6 . Except to say that he has "duly and consistently opposed admission of the letter,” the Secretary has not challenged the admissibility of this letter on appeal. Accordingly, we deem any argument that we should not now consider it to be waived. See United States v. Zannino, 895 F.2d 1, 17 (1st Cir.1990) (<HOLDING>). 7 . As has been explained in another context,
holding issues raised in notice of appeal but not briefed are deemed waived holding that issues not argued in initial brief are deemed waived holding that arguments which are not sufficiently developed are waived holding issues not raised in appellate brief are waived recognizing settled appellate rule that issues adverted to in a perfunctory manner unaccompanied by some effort at developed argumentation are deemed waived