Polar Tankers, Inc. v. City of Valdez, 557 U.S. 1 (2009), was a decision by the Supreme Court of the United States involving the tonnage clause of the United States Constitution. The City of Valdez in Alaska imposed a property tax that, in practice, applied only to large oil tankers. Polar Tankers, a ConocoPhillips subsidiary, sued, arguing that the tax violated the Tonnage Clause of the Constitution, which forbids a state, "without the Consent of Congress, [to] lay any Duty of Tonnage."