Litigants in a lawsuit over the future of ranching in the Point Reyes National Seashore are urging a federal court to stop residents of the park’s ranches and dairies from joining the case.

In responses filed last week in the U.S. District Court for the Northern District of California, both the National Park Service and the environmental organizations suing it opposed a motion by residents seeking a voice in the dispute. The ranchers, who themselves…