State preemption doesn't apply to BSU or any other public college in Idaho.
I.C. 18-3302J(5): "This section shall not be construed to affect:...
(c) The authority of the board of regents of the university of Idaho, the boards of trustees of the state colleges and universities, the board of professional-technical education and the boards of trustees of each of the community colleges established under chapter 21, title 33, Idaho Code, to regulate in matters relating to firearms."
Of course, the alleged "authority" of public colleges to ban the possession of firearms on campus is non-existent - Article I Section 11 of the Idaho Constitution doesn't make an exception for public colleges when it states that the rights of Idahoans to keep and bear arms shall not be abridged.
If you're trespassed from BSU for exercising your rights, that would seem to provide standing for a lawsuit asking for a declaratory judgment against BSU's no-firearms policy. (You can be trespassed from the BSU campus, and from city parks. Just try having a kegger in a city park or hanging out there after hours when it's closed.)
I'd say we should start by having an open-carry rally with signs saying "Support H.B. 222" while standing on the sidewalks adjacent to University Ave. The sidewalks are city-owned property, not university-owned, so BSU can't trespass you off like it can if you're on the quad. We should do this before the Senate State Affairs Committee hearing on the bill this week.