According to multiple dictionaries online: The intransitive verb _trespass_ means _violate_. The transitive verb tresspass also means violate. If you search for translations/conjugations of _tresspass_, _was trespassed_ is not listed (_was trespassing_ is, referring to the trespasser).

The _noun_ tresspass, on the other hand, can refer to the charge, the act itself, or a case regarding such. Perhaps this is what you're thinking of?

Etymology: the word tresspass is derived from crossing (violating) the law.

> Humans discussing trespassing in a legal context...

Legal definitions may not follow common definitions, but they generally don't contradict them. Legal language tends not to use words that have contradictory meanings (see: inflammable), as it makes it rather difficult to have a clear meaning.

> Cops and other legal personnel

Cops are not legal personnel, they are enforcers. They aren't trained in legal language.

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Dictionaries consulted: Webster's, Collins, American heritage, Cambridge, Cornell Wex, ecfr.gov, just about every dictionary I can find other than OED (requires payment) (most websites just quote one of the first three).

Further information on the use of tresspass in this way can be found at https://www.visualthesaurus.com/cm/dictionary/trespassers-wi...