JT
You are right parking in property is difficult to control
Due to the many quirks in the relevant laws
Rather than addressing the parking there are two solutions that work.
First gate the access but as we all know this is a pain for all.
The second is the law about access to property that is not gated and like it or not but the general public has right of access, like the door to door sales person that can access all floors.
But here is the solution
Revoking the implied licence to enter is a simple matter, a simple sign forbidding trespassing is all it takes to prevent access.
Now by being on the property a criminal act has occurred and yes the police do act on criminal actions.
In fact all legal recommendations is do not fight the trespasser call the police
Genuine visitors display a sign including lot visiting or get the same treatment as trespassers.