[1] Despite the Court upholding Section 201 unanimously, Potter Stewart, Warren Burger, and Harry Blackmun in a single opinion,[2] William J. Brennan, Byron White, and Thurgood Marshall in a separate single opinion,[3] and John Marshall Harlan II in a separate opinion argued the literacy test ban was constitutional under Section 2 of the 15th Amendment.

[6][7] The Court upheld Section 202 by an 8–1 ruling with Douglas and Brennan, White, and Marshall arguing the minimum residency duration requirement for voter registration and the uniform rule for absentee voting in presidential elections was constitutional under Section 5 of the 14th Amendment to enforce the Privileges or Immunities Clause.

[12][17] In a separate 5–4 ruling where Black joined Harlan and Stewart, Burger, and Blackmun to form the majority, the Court held that Section 302 lowering the voting age in state and local elections was unconstitutional under the 10th Amendment by the delegation of powers under the House Electors Qualifications Clause and the 17th Amendment,[6][18][12][17] while Douglas and Brennan, White, and Marshall argued it was also constitutional under Section 5 of the 14th Amendment to enforce the Equal Protection Clause.

[13][14] Less than seven months after Oregon v. Mitchell was decided, the Court's Section 302 holdings with respect to minimum age requirements as voter qualifications were superseded by the ratification of the 26th Amendment.

[19] In Arizona v. Inter Tribal Council of Arizona, Inc. (2013), the Court concluded that the Section 302 holding that permitted Congress to preempt state voter qualifications for minimum voting age in federal elections under the Equal Protection Clause was of minimal precedential value to that decision.