There are some interesting Ninth Circuit drug cases about whether flights or voyages between two points in the U.S. that cross international waters, such as California to Hawaii, are subject to warrantless customs inspections, as well as similar flights between Hawaii and Guam -- the latter complicated because it is a territory. I seem to recall that flights between Florida and New York were treated differently, at least before a Ninth Circuit en banc decision.

I've never had a First Amendment customs case. The CNMI controls its own customs borders, see 48 U.S.C. § 1801 note, as does Guam.