For more than a year and a half, Andrew Giacomini has been fighting to keep his clients in their homes in the Point Reyes National Seashore. The San Geronimo attorney has lost at nearly every turn.

Now, with the eviction deadline passed, he has refiled a lawsuit in federal court on behalf of displaced farmworkers and other ranch tenants—a last-ditch effort by a dwindling group of clients.

“We’re just trying to hang in there,” Mr.…