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...