Closed the exit / entrance to the garage, what to do?

Yesterday I was still going to write something on this topic, but was too lazy to sit down at 2 nights to write ...

Decided today

So a brief description of the situation:
I took off my garage for a motorcycle, at the request of the insurance company, the usual garage in the yard. When for the first time, a kind person left his car at the gate, I wrote an advertisement asking not to put the car at the gate.
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It helped for a while, with exceptions, but it seemed to help, and now, for the second day in a row, I arrive at around 11-12 at night, the car is at the gate, with transits and without signaling, in any case, it doesn’t react to knocking on the wheels, yesterday decided to leave a note , with a mobile phone, with a request to call at least when he removes, did not receive a call, but in 2 nights the entrance was open ...

And so the question is, who has what experience in motivating others to observe nickeys and elementary bases of mutual respect ...

PS Suggestions for action, preferably without administrative and criminal liability.