An internal Environmental Protection Agency memo obtained by the environmental group Greenpeace suggests uncertainty created by the Supreme Court’s 2006 Rapanos decision has had a negative effect on federal enforcement in wetlands cases. The ruling dealt with the scope of federal wetlands jurisdiction.

According to a March 4 memo from Granta Nakayama, EPA assistant administrator in charge of enforcement, the agency chose not to enforce as many as 300 potential Clean Water violations between July 2006 and December 2007 because of regulatory uncertainty after Rapanos.

Two House committee chairmen wrote to EPA Administrator Stephen Johnson on July 7, demanding more information. EPA says it will cooperate with the lawmakers.