922(o) -- or NFA -- held void for vagueness as applied to LEO
A district court has ruled in US v. Vest, dismissing the indictment (pdf file). The charge was possession of a machinegun in violation of 18 USC 922(o) and without proper registration under NFA, and the defendant was a police officer.
Apparently, he got the MG for use in official duty, certifying it as such (getting around 922(o)'s ban), and registering it as such. The prosecution argument was that 922(o) makes an exception for possession by a police dept or under authority of such a dept, and that that didn't cover personal ownership by an officer, but only by the PD.
Court found the requirement void for vagueness as applied (that is, under these particular circumstances, not under any possible circumstances).