The Trump administration said Wednesday it will attempt to add a citizenship question on the 2020 census while complying with the Supreme Court’s ruling in Department of Commerce v. New York. Five justices held that the Census Act allows the question, but a separate five-justice majority found the rulemaking that added the question was procedurally deficient. There is a way forward. The Constitution itself requires the collection of citizenship information.

Section 2 of the 14th Amendment provides that if a state denies the franchise to anyone eligible to vote, its allotment of House seats shall be “reduced in the proportion which the number of such . . . citizens shall bear to the whole number of . . . citizens . . . in such state.” This language is absolute and mandatory. Compliance is impossible without counting how many citizens live in each state.

The 14th Amendment was adopted in 1868, and this provision meant to secure the voting rights of newly freed slaves. But it wasn’t limited to that purpose. An earlier version of Section 2, introduced in 1865, specifically referred to limits on suffrage based on “race or color,” but the Senate rejected that limitation. The amendment forbids state interference with the rights of all eligible voters (then limited to males over 21).