The Commonwealth of Puerto Rico is governed under a constitution of 1952, as amended. An amendment to the constitution may be proposed by the commonwealth’s legislature or by a constitutional convention. To become effective an amendment must be approved by a majority of persons voting on an issue in an election. Puerto Ricans share most rights and obligations of other U.S. citizens; residents of the commonwealth may not vote in U.S. presidential elections, and, except for federal employees and members of the U.S. armed forces, are not required to pay federal income taxes.