The Double Jeopardy Clause bars Puerto Rico and the United States from successively prosecuting a single person for the same conduct under equivalent criminal laws. Puerto Rican prosecutors indicted the defendant for illegally selling firearms in violation of the Puerto Rico Arms Act of 2000. While those charges were pending, federal grand juries also indicted them, based on the same transactions, for violations of analogous federal gun trafficking statutes. The Court held that the separate sovereign doctrine (double jeopardy does not bar successive prosecutions if they are brought by separate sovereigns) did not apply. If two entities derive their power to punish from independent sources, then they may bring successive prosecutions. Conversely, if the entities draw their power from the same ultimate source, then they may not. While States are separate sovereigns from the federal government, Puerto Rico is not.