I don’t know of their legality, but a bunch here were recently booted from a house they were living in.
The pipes had burst some time ago, and they were living above a basement that was 3/4 full of sewage.
Hmmm.... If it had a septic system, it probably couldn't handle the load. The diffusing pipes would become blocked and the sewerage would back up. Every time you flush or bathe it comes out in the lowest drain in the house, usually in the basement near the laundry.
We had a spell of -10 F (daily high, can't wait for global warming) for about a week a couple of winters ago and the pipes leading to the leeching field froze (improper installation, unevenly laid pipes), we couldn't use our plumbing for a couple of days..
These people would rather live in a house full of sewage in the States then live in their own country. I guess that says a lot for the country they came from.