The Court's early decisions under the Fifteenth Amendment established that it imposes but one limitation on the powers of the States. It forbids them to discriminate against Negroes in matters having to do with voting. See Ex parte Yarbrough, 110 U. S. 651, 110 U. S. 665; Neal v. Delaware, 103 U. S. 370, 103 U. S. 389-390; United States v. Cruikshank, 92 U. S. 542, 92 U. S. 555-556; United States v. Reese, 92 U. S. 214. The Amendment's command and effect are wholly negative. 'The Fifteenth Amendment does not confer the right of suffrage upon any one,' but has 'invested the citizens of the United States with a new constitutional right which is within the protecting power of Congress. That right is exemption from discrimination in the exercise of the elective franchise on account of race, color, or previous condition of servitude.' Id. at 92 U. S. 217-218.
Decisions have made clear that action by a State that is racially neutral on its face violates the Fifteenth Amendment only if motivated by a discriminatory purpose. In Guinn v. United States, 238 U. S. 347, the Court struck down a 'grandfather' clause in a ...