The Constitution refers to slaves and slavery but only uses the word slavery once, in the Thirteenth Amendment.
Article 1 Section 2 says: Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers, which shall be determined by adding to the whole Number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Persons.
Article 1 Section 9 says: 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.
Article 4 Section 2 says: No Person held to Service or Labour in one State, under the Laws thereof, escaping into another, shall, in Consequence of any Law or Regulation therein, be discharged from such Service or Labour, But shall be delivered up on Claim of the Party to whom such Service or Labour may be due.
The 15th Amendment says: The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of race, color, or previous condition of servitude.
All of these references to “persons” are understood to be talking about slaves. But has anyone ever tried to play dumb and make a legal argument based on some other possible interpretation of these passages?
I know this has been done with the 13th and 14th Amendments. People have, for example, argued against the military draft by claiming it is “involuntary servitude” (these arguments have been dismissed). And a whole bunch of legal cases having nothing to do with slavery have been based on the “equal protection” clause of the 14th (many of which have succeeded).