Spotted owl's analogy correct to a large extent. Just saying it don't make it so. I always chuckle when I see signs that say something like "Not responsible for injury sustained on these premises" or similar. These signs have zero legal effect, or nearly zero, if negligence is otherwise present, because they don't amount to an assumption of the risk - doesn't meet all the elements, particularly if the person didn't in fact actually see the sign. They DO help the owner to some extent, I'm sure, simply by discouraging claims/lawsuits, because the general public *believes* that their claim would be fruitless, if they make a decision before talking to a lawyer. As the man said, if they said "We are not responsible if we murder you while on these premises" has the about the same effect as "your vehicle is subject to search.", in the criminal law realm. Having said that as a general proposition, *IF* it could be shown that you actually saw the sign and read it, then you may have formed a contract - "i'll let you enter if you give permission to search" - which gives rise to the premises owner a right *civilly* to search. BUT you could still refuse the proffered search, and their only remedy would be a claim for money damages for breach of contract - they could not force a search if it would damage your property or be a breach of the peace to do so (i.e. if you're fighting them off physically to prevent the search). If you refused search, then and only then could they demand a 'cease and desist', and give you an opportunity to leave, before they could pass over from the civil realm into the criminal realm, and make a charge for trespassing. Now, *assuming* that a contract was formed, and *assuming* that you assented to the search to meet your contractual duty, then *IF* something illegal was found, then it could be handed over to the police on a criminal referral for prosecution, of course. So now then the question becomes, what if your car is locked, and they damage your property to open it, and find contraband? Could they hand over evidence to the police, for a valid criminal prosecution? Yes, unfortunatly your only remedy would be suing them for damage to your property civilly. If your car is unlocked, and you've *already* assented to a search by virtue of forming a contract by reading the sign and then entering, then sure they've got a right to search it without further permission. BUT, if you didn't actual form a contract; i.e. if your defense is, I never saw the sign, therefore a contract was never formed, and their illegal search results in a criminal prosecution, then you'd have a right to sue them civilly for a tort of invasion of privacy or similar, and your damages would be, in theory, all of the costs of your criminal charge defense, fines/restitution, and compensation for jail time served. But it would not relieve you of your criminal liability (assuming that it is, in fact, against the criminal law to possess a firearm on a school's premises in your state).