June 21, 1915 The United States Supreme Court in Guinn v. United States ruled that the grandfather clauses in the constitutions of Maryland and Oklahoma were unconstitutional. The ruled that “the grandfather clauses in the Maryland and Oklahoma constitutions to be repugnant to the Fifteenth Amendment and therefore null and void.” The Oklahoma constitution allowed an exemption to the literacy requirement for those voters whose grandfathers had either been eligible to vote prior to January 1, 1866, or was then a resident of some foreign nation, or were soldiers. This disenfranchised black voters because most of their grandfathers had been enslaved and therefore unable to vote before 1866. The ruling also affected similar provisions in the constitutions of Alabama, Georgia, Louisiana, North Carolina, and Virginia. As a result of the ruling, state legislatures immediately passed new statues meant to restrict black voter participation.