has employed the taxing power in uses other than solely for the raising of revenue, such as: regulatory taxation – taxing to regulate commerce; prohibitive taxation – taxing to discourage, suppress, or even exterminate commerce; obligation taxation – encouraging participation in commerce via taxation on those not participating in interstate commerce; e.g. the Patient Protection and Affordable Care Act, "Chief Justice Roberts concluded in Part III–C that the individual mandate must be construed as imposing a tax on those who do not have health insurance"; tariffs – taxing as a means of protectionism. In 1922, the Supreme Court struck down a 1919 tax on child labor in Bailey v. Drexel Furniture Co., commonly referred to as the "Child Labor Tax Case". The Court had previously held that Congress did not have the power to directly regulate labor, and found the law at issue to be an attempt to indirectly accomplish the same end. This ruling appeared to have been reinforced in United States v. Butler, in which the Supreme Court of the United States ruled that the processing taxes instituted under the 1933 Agricultural Adjustment Act were an unconstitutional attempt to regulate state activity in violation of the Tenth Amendment. However, despite its outcome, Butler affirmed that Congress does have a broad power to tax, and to expend revenues within its discretion. Implicit power to spend With the power to tax implicitly comes the power to spend the revenues raised thereby in order to meet the objectives and goals of the government. To what extent this power ought to be utilized by the Congress has been the source of continued dispute and debate since the inception of the federal government, as will be explained below. However, interpretations recognizing an implicit power to spend arising specifically from this clause have been questioned, with the Necessary and Proper Clause being suggested as the actual source of Congress's spending power. The Supreme Court has also found that, in addition to the power to use taxes to punish disfavored conduct, Congress can also use its power to spend to encourage favored conduct. In South Dakota v. Dole, the Court upheld a federal law which withheld highway funds from states that did not raise their legal drinking age to 21. Limitations on taxing power Several Constitutional provisions address the taxation and spending authority of Congress. These include both requirements for the apportionment of direct taxes