provisions of the Amendment are to be construed in light of this fundamental purpose. In its decision the Court said: Section 1 has been the most frequently litigated part of the amendment, and this amendment in turn has been the most frequently litigated part of the Constitution. Citizenship Clause The Citizenship Clause overruled the Supreme Court's Dred Scott decision that black people were not citizens and could not become citizens, nor enjoy the benefits of citizenship. Some members of Congress voted for the Fourteenth Amendment in order to eliminate doubts about the constitutionality of the Civil Rights Act of 1866, or to ensure that no subsequent Congress could later repeal or alter the main provisions of that Act. The Civil Rights Act of 1866 had granted citizenship to all people born in the United States if they were not subject to a foreign power, and this clause of the Fourteenth Amendment constitutionalized this rule. According to Garrett Epps, professor of constitutional law at the University of Baltimore, "Only one group is not 'subject to the jurisdiction' [of the United States] – accredited foreign diplomats and their families, who can be expelled by the federal government but not arrested or tried." The U.S. Supreme Court stated in Elk v. Wilkins (1884) with respect to the purpose of the Citizenship Clause and the words "persons born or naturalized in the United States" and "subject to the jurisdiction thereof" in this context: There are varying interpretations of the original intent of Congress and of the ratifying states, based on statements made during the congressional debate over the amendment, as well as the customs and understandings prevalent at that time. Some of the major issues that have arisen about this clause are the extent to which it included Native Americans, its coverage of non-citizens legally present in the United States when they have a child, whether the clause allows revocation of citizenship, and whether the clause applies to illegal immigrants. Historian Eric Foner, who has explored the question of U.S. birthright citizenship to other countries, argues that: Garrett Epps also stresses, like Eric Foner, the equality aspect of the Fourteenth Amendment: Native Americans During the original congressional debate over the amendment Senator Jacob M. Howard of Michigan—the author of the Citizenship Clause—described the clause as having the same content, despite different wording, as the earlier Civil Rights Act of 1866, namely, that it excludes