Lawrence Lessig refers to
Article I, sec. 8, cl. 8 of the U.S.
Constitution as the monopolies clause. That clause authorizes Congress "To promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries."
Jefferson himself thought of what we now call
intellectual property as a government-granted monopoly.
Sadly, courts have not yet read the purpose part of the monopolies clause as a limitation on Congressional action. See the Eldred v. Reno/Ashcroft litigation over the constitutionality of the Sonny Bono Copyright Term Extension Act.