Which states are suppressors legal in? Particularly, are they legal in Idaho without permits? (Sound Suppressors)

There are a number  of states that permit those who are properly licensed to possess sound suppressors/silencers, ID among them IIRC. In fact,  Gemtech ([url]www.gem-tech.com[/url]), one of the manufacturers of such devices, is located in Boise. But suppressors are tightly regulated by the feds, just like full-auto weapons, so possessing one without the requisite licenses is a felony. Too bad, because noise is one of the few drawbacks to guns IMHO. [;)]
(Edited for punctuation)

For info, BATF considers a sound suppressor to be a flash suppressor, too.  It counts as an "evil feature", so you can't fit one to a post ban semi-auto firearm capable of accepting a detachable magazine if it already has one "evil feature."