IANAL, but this is my understanding...
They were apparently manufactured from 1992-2005.
A threaded barrel on a firearm manufactured prior to 9/13/94 would be OK.
A threaded barrel on a firearm manufactured after 9/13/94 is not OK. The threads would need to be removed or permanently covered. The most common way is to have a gunsmith permanently install a muzzle brake (not a flash hider, as they are also illegal in NY).