In the 1907 case of Kent v. People of Porto Rico, the U.S Supreme Court examined whether a tax imposed by Puerto Rican authorities on imported goods from mainland United States was constitutional under the Foraker Act (Organic Act) of 1900. The act established civil government in Puerto Rico and stipulated that all statutory laws applicable to territories would also apply to Puerto Rico unless specifically exempted by Congress. Charles R. Kent, an importer based in San Juan, argued that this tax violated his rights as it treated trade between US states and territories differently than trade within mainland America. The court ruled against Kent stating that although Puerto Rico was subject to American sovereignty after its acquisition following Spanish-American War, it remained a foreign territory for purposes related to revenue laws until Congress explicitly stated otherwise. Therefore, import duties could be levied on goods coming into Puerto Rico from other parts of the United States without violating any constitutional provisions or federal law.

In the dissenting opinion for Kent v. People of Porto Rico, Justice Harlan argued that the Foraker Act did not give Congress unlimited power over Puerto Rico. He believed that while it was within Congress's authority to establish a civil government in Puerto Rico, this should be done with respect for the fundamental rights and liberties of its people as outlined in the U.S Constitution. Harlan disagreed with the majority's view that these constitutional protections did not extend automatically to territories acquired by America. He asserted that once territory becomes part of America, all constitutional guarantees apply there just as they do on mainland USA - including protection against unreasonable searches and seizures (Fourth Amendment) or double jeopardy (Fifth Amendment). Therefore, he concluded that Mr.Kent’s conviction violated his Fifth Amendment right against double jeopardy because he had been tried twice for same offense: first under military law then again under civil law after transfer of sovereignty from Spain to US.