Can you use a semi-automatic assault rifle to hunt big game (deer, elk, bear, etc.)?

Yes you can, as long as it complies with the other restrictions in code and rule, (copied below). There is no restriction in idaho on the number of rounds a firearm can carrry, or restrictions against use of semi-automatics. 410.UNLAWFUL METHODS OF TAKE. No person shall take big game animals as outlined in this section. (7-1-93) 01. Firearms. (7-1-93) a. With any firearm that, in combination with a scope, sling, and/or any other attachments, weighs more than sixteen (16) pounds. (7-1-93) b. With any shotgun using any shot smaller than double-aught (#00) buck. (7-1-93) c. With any rimfire rifle, rimfire handgun or any muzzleloading handgun, EXCEPT for mountain lion and trapped gray wolf. (4-4-13) d. With a fully automatic firearm. (10-26-94) e. With any electronic device attached to, or incorporated in, the firearm (including handguns and shotguns) or scope; except scopes containing battery powered or tritium lighted reticles are allowed. (4-2-08) - Josh Royse, Regional Conservation Officer, Magic Valley Region