The U.S. Supreme Court case Polar Tankers, Inc. v. City of Valdez, Alaska (2008) revolved around a tax dispute between the city of Valdez and Polar Tankers, a shipping company that transported oil from the Port of Valdez to refineries in other states. The city had imposed a personal property tax on large vessels like those owned by Polar Tankers which were not used for local commerce but docked at its port occasionally throughout the year for loading purposes only. The court ruled 7-2 in favor of Polar Tankers stating that this taxation was unconstitutional under the Tonnage Clause as it essentially amounted to charging ships for "the privilege" of entering their harbor or using their ports - something prohibited by federal law unless approved by Congress.

The dissenting opinion in the case of Polar Tankers, Inc. v. City of Valdez, Alaska argued that the tax imposed by the city was not discriminatory or inconsistent with established principles of fair apportionment. The justices contended that it was a legitimate property tax on vessels benefiting from local services and protections provided by Valdez, such as harbor maintenance and emergency response capabilities. They also pointed out that other businesses operating within city limits were subject to similar taxes based on their property value. Furthermore, they disagreed with the majority's interpretation of "tonnage" under Tonnage Clause jurisprudence; arguing instead for a narrower understanding which would exclude general property taxes like those levied by Valdez.