The decision of the Port of San Diego and the cities of Imperial Beach and Chula Vista to sue the U.S. branch of the binational International Boundary and Water Commission for allegedly violating the federal Clean Water Act is a proportionate, necessary response to a grave problem that only seems to get worse, not better. The port and the cities say they can no longer tolerate the commission’s failure to prevent sewage, trash, industrial waste and pesticides from flowing through the Tijuana River and into the Pacific Ocean on the U.S. side of the border.