"the Democratic Congress will challenge the president’s non-enforcement of the laws.”

Pelosi threat to sue Bush over Iraq bill | By Jonathan E. Kaplan and Elana Schor | May 09, 2007

House Speaker Nancy Pelosi (D-Calif.) is threatening to take President Bush to court if he issues a signing statement as a way of sidestepping a carefully crafted compromise Iraq war spending bill.
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“The president has made excessive use of signing statements and Congress is considering ways to respond to this executive-branch overreaching,” a spokesman for Pelosi, Nadeam Elshami, said. “Whether through the oversight or appropriations process or by enacting new legislation, the Democratic Congress will challenge the president’s non-enforcement of the laws.”

It is a scenario for which few lawmakers have planned. Indicating that he may consider attaching a signing statement to a future supplemental spending measure, Bush last week wrote in his veto message, “This legislation is unconstitutional because it purports to direct the conduct of operations of the war in a way that infringes upon the powers vested in the presidency.”
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In order to hear an argument, a federal court would have to grant what is known as “standing,” meaning that lawmakers would have to show that Bush is willfully ignoring a bill Congress passed and that he signed into law. ...