As I understand it, "to be trespassed" is a term of art that basically means "the cops were called, told that person was trespassing, the cops duly informed that person they are trespassing & had to leave the property, and the person left, but was not charged". It's basically establishing a legal trail so that if the person refuses to leave or continues to trespass at that location in the future they have a better basis for charging them.
It seems to be a real definition, see definition 6 under etymology 2:
> (transitive, law, especially New Zealand)[1] To subject [someone] to a trespass notice, formally notifying them that they are prohibited from entry to a property, such that any current or future presence there will constitute trespass, (especially) criminal trespass
Ah, I thought that could be the case but didn't see it listed in Merrium-Webster [0]. Seems like it is legal jargon, so might be better to use plain language here.
You have to be informed that you're not allowed to be on the premises ("trespassed") and be allowed to leave before you can be charged with trespassing.
I have heard my friends here in the USA say it about someone locally who is known to cause trouble with businesses. I had never heard it said that way until they said it that way.
It's colloquially used like that in the blackjack community. "Being trespassed" by a casino means the casino informs you that you must leave and that if you return, you will be guilty of trespassing.