To help Washington retailers compete with retailers in states with no sales or use tax, Washington State passed a statute taxing the use of personal property in Washington if purchased in another state. The statute provided credits for tax already paid to Washington or another state. Silas Mason Co. (plaintiff) was hired to construct a dam in Washington, and consequently brought into Washington equipment purchased in other states. Henneford (defendant), the Tax Commission of Washington, charged Silas Mason Co. a 2 percent use tax on said equipment. A district court found the statute to be void on its face, and granted an interlocutory injunction. This case comes on appeal to determine if the statute violates the Commerce Clause of the Constitution.