CHEYENNE, Wyo. (AP) — A federal judge is allowing wild horse advocacy groups to intervene in a lawsuit in which livestock operators are trying force the removal of wild horses from private lands in an area of roughly 2 million acres in southwestern Wyoming.

U.S. District Judge Scott Skavdahl presides over the Rock Springs Grazing Association's lawsuit. The association wants to force the U.S. Bureau of Land Management to remove horses from private lands along the so-called "checkerboard area."

The association says BLM has ignored a 30-year-old agreement to limit horse numbers.

Skavdahl in November allowed the International Society for the Protection of Mustangs and Burros, the American Wild Horse Preservation Campaign and the Cloud Foundation to intervene. He denied a similar request from the Wyoming Stock Growers Association and other groups this month.