Just open carry, if they ask you to leave then leave. The only places you can't carry is in the post office, military bases, and court houses.
Carry not allowed in Juvenile Justice Facility, jail, or a public or private K-12 school.
Also note 18-3302:
(9) While in any motor vehicle, inside the limits or confines of any city, a person shall not carry a concealed weapon on or about his person without a license to carry a concealed weapon. This shall not apply to any firearm located in plain view whether it is loaded or unloaded. A firearm may be concealed legally in a motor vehicle so long as the weapon is disassembled or unloaded.
The above information is incorrect and/or inaccurate in regards to carry in a courthouse, jail, public or private K-12 schools.
INAL, but here's the low-down:
Idaho Code only restricts conceal carry at courthouses. Open carry is legal (however, read more on this below).
There is no state statute restricting OC or CC in city or county jails; nor can a city or a county pass policy/law governing such.
OC/CC is allowed at a private or public K-12 school when there is no "activity sponsored by or through the school" occurring, or when you are in your vehicle picking up or dropping off your kid(s). OC/CCin'g, say, on a Sunday Morning while one walks their dog, as long as there's no "activity sponsored by or through the school" occurring, one may discern of their own as to whether to OC/CC at that time on school property (mind you, an Idaho CPW *IS* required to do such, otherwise a 5-year federal felony). Mind you, IMHO, "school" means the school itself, not the school district. Mind you #2: I'm not aware of any State or Federal (Idaho-only) case law on this.
OC/CC *CAN* occur at/on a private or public K-12 during "activity sponsored by or through the school" *WHEN* a school board authorizes a person to do so.
Back to courthouses ~ District Administrative Judges (DAJ) have "legislated from the bench" and passed "regulations" prohibiting OC in courthouses. Several DAJ's have extended that "rule" to cover non-court divisions and/or other county functions/departments. This is a prime example of where no authority has been given and the gov't takes control of what they are not authorized to do. I am aware this is presently being considered to be legall challenged in the County of Ada. As well, a state law is may be considered in the 2013 Legislative session wherein it would ban judges from "legislating from the bench" as such.
The Idaho State Board of Corrections is authorized to "administrate" "correctional facilities" (e.g., prisons; a building where a person is incarcerated overnight and *DOES NOT* include a day-only holding cell location such as, oh, I dunno, a District Parole Office like the one near the Stereo Shoppe on Fairview in Boise, ID), yet has extended that "authorization" to cover *all* Idaho Department of Corrections property and buildings, even the Administration building which is no where near a "correctional facility" (but, one could say it kinda looks like one!!). I am aware this is presently being considered to be legally challenged in state District Court.
The shorter answer in all this is that Idaho's Constitution, Article I, Section 1, reads:
INALIENABLE RIGHTS OF MAN. All men are by nature free and equal, and have certain inalienable rights, among which are enjoying and defending life and liberty; acquiring, possessing and protecting property; pursuing happiness and securing safety.
The question presented is: How can one go about "defending life" and "securing safety" when they are prohibited from doing such?
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Carry on, then!