such regulations do not conflict with federal law. State laws related to commerce powers can be valid if Congress is silent on the matter. Ableman v. Booth, State courts cannot issue rulings that contradict the decisions of federal courts. Texas v. White, The states that formed the Confederate States of America during the Civil War never actually left the Union because a state cannot unilaterally secede from the United States. Hans v. Louisiana, The Eleventh Amendment bars suits by citizens against their own state in federal court. Pollock v. Farmers' Loan & Trust Co., Income taxes on interest, dividends, and rents are, in effect, direct taxes that must be apportioned among the states according to their populations. This decision was voided by the Sixteenth Amendment in 1913, allowing income taxes to be implemented without apportionment. Swift and Company v. United States, Congress can prohibit local business practices in order to regulate interstate commerce because those practices, when combined, form a "stream of commerce" between the states (superseded by National Labor Relations Board v. Jones & Laughlin Steel Corporation (1937)). Hunter v. City of Pittsburgh, States have sovereignty over their local governments. Ex parte Young, When state officers are charged with violating federal law, they cannot set up the state's federal constitutional sovereign immunity to defeat suits for prospective relief. Missouri v. Holland, Treaties made by the federal government are supreme over any concerns brought by the states about such treaties interfering with any states' rights derived from the Tenth Amendment. United States v. Wheeler, The Constitution grants to the states the power to prosecute individuals for wrongful interference with the right to travel. United States v. Butler, The U.S. Congresss power to lay taxes is not limited only to the level necessary to carry out its other powers enumerated in Article I of the U.S. Constitution, but is a broad authority to tax and spend for the "general welfare" of the United States. National Labor Relations Board v. Jones & Laughlin Steel Corporation, The National Labor Relations Act and, by extension, the National Labor Relations Board are constitutional because the Commerce Clause applies to labor relations. Therefore, the NLRB has the right to sanction companies that fire or discriminate against workers for belonging to a union. Also, a local commercial activity that is considered in isolation may still constitute interstate commerce if that activity has a "close and substantial relationship"