In the state where I live, landlord and tenant relationships are not completely logical. A local recycling business, they grind old trees into mulch, allowed a group of homeless people to camp on his land. After they began to pose a serious fire risk, he asked them to leave. He was informed by police that this could not be considered trespassing, since they had permission at one point, and instead he would need to work through eviction, often a 60-180 day process.
Similarly, several families have returned from vacation to find other people had moved into their houses. Rather than this being a simple matter of trespass, and having them removed, the families are staying in hotels while working through eviction proceedings. The families can sue the squatters for damages, assuming they prevail on eviction, but it is unlikely that there are any assets worth seizing.
I am working with a paralegal currently, and may try to find lawyers sympathetic to this cause to ensure that once the time is up, I can compel my guests to leave, and that is house rules are blatantly disregarded, that eviction is not required for removal.
I truly hope that I never need to remove someone against their will, but, as these are people I do not know, I must be prepared just in case.