Read the 5th & 6th Amendments. -- Due process must be followed in trials before impartial juries informed of "-- the nature and cause of the accusation --".
The question of whether the law against possessing machine guns is constitutional is part of "the accusation".
The question of whether the law against possessing machine guns is constitutional is one the defense can raise before the judge; if they lose, they can raise it on appeal.
'Legalistic' nonsense. -- If an informed jury decides the 'law' does not apply to the case at issue, the defendant is free.
But our system, as currently set up, does not permit juries to hear arguments on the constitutionality of laws.
Our 'system' is set up to ignore the 5th & 6th amendments and to prevent jury nullification; - that aspect of it is unconstitutional in itself.
[A judge said that a] "lawyer couldn't argue constitutional issues in front of the jury, which is a correct ruling under current law."
"Currant law" is the issue here. Arguing that 'the law is the law' is simply specious legalistic babble.
I too believe that the constitutionality of a law is certainly fair game before a jury. If the law is not constitutional, the jury should not be bound by only the law itself. I do not believe in jury nullification, though unless they believe the law to be unconstitutional. Otherwise it is a formula for chaos.