The U.S. Supreme Court on June 23 declined to hear a challenge by two environmental groups to the Dept. of Homeland Security’s plan to build a fence on parts of the U.S. border with Mexico.

In their petition, Defenders of Wildlife and the Sierra Club contended that DHS Secretary Michael Chertoff’s waiver of 19 federal environmental statutes to expedite the fence’s construction was unconstitutional. The groups focused on a fence segment in the San Pedro Riparian National Conservation Area in Arizona. The waiver was carried out under the 2005 REAL-ID Act.

DHS plans to complete 670 miles of pedestrian and vehicle fence on the southern border by the end of 2008. Of that, DHS says 331 miles were completed as of June 13.