Entrapment is the state coercing someone to do something they would not do under normal circumstances. It sounds to me as if these people are illegally parking under normal circumstances. The rules about curbs, hydrants, driveways, &c are well known and common enough between every state that there is no excuse that they weren't aware this was illegal.
They made the parking rules unclear and never enforced them then cracked down brutally.
Most places do not make the rules unclear and many rules brought up in the subthread, e.g. hydrants and parking near an intersection, are well known and common among the states.
Look, I'm not saying that basically giving everyone a month with no warnings and then going out in force isn't a crappy thing to do. I'm just saying that that's not entrapment, nor is an an awful thing for the police to do, even if there are nicer ways to do it, e.g. giving notices on windshields for the first week of the semester and afterwards being issuing tickets.
It's still highly unethical, especially when your target population is supposedly already paying tens of thousands for use of the facilities.
City streets are not the campus facilities, and what of the people using public transit or other means of transportation? Should they have to pay additional on their tens of thousands to subsidize those people with cars?
They aren't the law either any more than Jimmy's Pizza place is when the call to tow a car that was abandoned for a week.