Check this out: lawprof Ilya Somin has posted "Squatters' Rights Laws Violate the Takings Clause" at Volokh.
His thesis is just as the title suggests, arguing that state statutes that treat trespassers as tenants are government-authorized physical occupations, and thus are takings:
Ideally, state and local governments should make it easy for property owners to swiftly remove squatters, and should subject the trespassers to civil and criminal sanctions. But where they instead facilitate this violation of property rights, the laws that do so violate the Takings Clause of the Fifth Amendment, which requires payment of "just compensation" whenever the government takes "private property."
Professor Somin relies on Cedar Point, and addresses the narrow exception to the general rule from that case that all physical invasions and occupations are takings without regard to the diminution in use or value or the owner's expectations, where the government had enabled the same access as does the "traditional common law."
The common law knows about adverse possession, he writes, where a trespasser may gain a property right, but only after meeting fairly rigorous legal tests, where the owner has actual notice of the possession and its adversity to her property rights. These squatter statutes go much further, because they force property owners unwillingly to become lessors.
In other cases where the courts have upheld regulations and restrictions on an owner's right to recover possession from an actual tenant -- you know, someone with whom the owner actually and expressly agreed, and then transferred the right to exclude to the tenant -- the courts frequently note that "no one is forcing you to become a landlord."
Well here, the owner is being forced to become a landlord.
Professor Somin wraps by noting, "I hope property owners and public interest law firms give serious consideration to bringing takings challenges against these laws. They are not a panacea for the problem. But they could help."
Since we are part of a non-profit, pro bono, public interest law firm as the good professor describes, we shall note here that the welcome mat is out, and if the above-situation is your situation, let us know.