We do offer a sign with text - Air Will be Taken Out of Tires - License Plates Removed From Unauthorized Parkers. However, it depends on your local laws and jurisdiction whether you can actually take such steps against vehicles illegally parked on your private property. Most lawyers say that touching a vehicle and deflating the tires is considered “vandalism”. As a private parking owner, the only aim should be to remove the vehicle off your property and not to damage it. In New York, deflating the tires can fall under “Criminal Tampering” (§ 145.14) and is punishable by law. Posting a warning sign about it would not harm you and will in fact discourage people from wrongly parking.