The California Motor Vehicle Fuel License Tax Act imposes a license tax, measured by gallonage, on the privilege of distributing any motor vehicle fuel. The Act is inapplicable 'to any motor vehicle fuel sold to the government of the United States or any department thereof for official use of said government.' P sold gasoline to the United States Army Post Exchanges in California. The State levied a tax, and P paid it under protest. P sued D on two grounds: (1) that sales to the Exchanges were exempt from tax; (2) that, if construed and applied to require payment of the tax on such sales, the Act would impose a burden upon instrumentalities or agencies of the United States contrary to the Federal Constitution. The trial court ruled for D. The Supreme Court of California affirmed. P appealed.