BOISE, Idaho -

A federal judge says a Boise-area hospital violated federal antitrust laws when it purchased Idaho's largest independent physicians' practice.

U.S. District Judge B. Lynn Winmill made the ruling Friday, ordering St. Luke's Health System to undo its buyout of the Nampa-based Saltzer Medical Group.

The ruling came in a lawsuit between St. Luke's, Saint Alphonsus Regional Medical Center and the Federal Trade Commission. The FTC and Saint Alphonsus alleged the buyout was an illegal market grab that gives St. Luke's an unfair advantage, but attorneys for St. Luke's countered that the acquisition would improve patient care and give consumers more options.

Winmill said that it's likely the buyout would raise health care costs because it would give St. Luke's a dominant market position.