 Puerto Ricans became citizens of the United States as a result of the passage of the Jones–Shafroth Act of 1917.Since this law was the result of Congressional legislation, and not the result of an amendment to the United States Constitution, the current U.S. citizenship of Puerto Ricans can be revoked by Congress, as they are "statutory citizens", not "14th Amendment citizens".The Jones Act established that Puerto Ricans born prior to 1899 were considered naturalized citizens of Puerto Rico, and anyone born after 1898 were U.S. citizens, unless the Puerto Rican expressed his/her intentions to remain a Spanish subject.