U.S. Constitution, Article I — The Legislative Branch, Section 9, Clause 1
The Migration or Importation of such Persons as any of the States now existing shall think proper to admit, shall not be prohibited by the Congress prior to the Year one thousand eight hundred and eight, but a Tax or duty may be imposed on such Importation, not exceeding ten dollars for each Person.
Notes
Bars Congress from prohibiting, before the year 1808, the migration or importation of such persons as any existing state thinks proper to admit. Allows a tax or duty on such importation of no more than ten dollars per person, so the limit on federal action was tied to a fixed date.
Use as reference
Lexinter.net | U.S. Const. art. I, § 9, cl. 1 | https://laws.lexinter.net/constitution/us/article-1/section-9/clause-1