In Railway Express Agency, Inc. v. Virginia (1958), the US Supreme Court ruled on a case involving interstate commerce and state taxation rights. The appellant, Railway Express Agency, was an interstate carrier that also conducted business within Virginia's borders. The company challenged a tax imposed by the state of Virginia on its gross receipts from intrastate business activities arguing it violated the Commerce Clause of the U.S Constitution as it discriminated against interstate commerce. The court disagreed with this argument and upheld Virginia’s right to impose such taxes stating that there was no discrimination since all businesses operating in-state were subject to similar taxes regardless if they engaged in both intra- and inter-state commerce or solely intrastate operations. This decision affirmed states' rights to levy taxes on companies conducting business within their boundaries without violating federal law provided these laws do not discriminate against out-of-state entities or impede free trade among states.

In the dissenting opinion for Railway Express Agency, Inc. v. Virginia, Justice William O. Douglas argued that the law in question was not applied equally to all parties and therefore violated the Equal Protection Clause of the Fourteenth Amendment. He contended that while it is within a state's rights to regulate businesses for public safety reasons, such regulations must be applied uniformly without discrimination or favoritism towards certain groups or individuals over others. In this case, he believed that Virginia had unfairly targeted out-of-state corporations like Railway Express Agency by imposing stricter regulations on them than those imposed on local businesses conducting similar operations within its borders.