On October 1, the U.S. Supreme Court agreed to hear Puerto Rico v Valle, 15-108. Technically the case is about criminal law, but the courts, to resolve this case, must also resolve whether Puerto Rico has any sovereignty or whether Congress has all sovereignty over Puerto Rico.
A resident of Puerto Rico was indicted by the federal government for the illegal sale of firearms. He plead guilty and served a short term. Then he was indicted by Puerto Rico authorities for the gun violation. The Puerto Rico Supreme Court ruled that he could not be prosecuted by Puerto Rico because that would be double jeopardy. The double jeopardy part of the U.S. Constitution prevents the same government from prosecuting someone twice for the same offense, but it does not prevent both the federal government and a state government from prosecuting. Thus the question turns on whether Puerto Rico has a sovereign (even if limited) government of its own. Here is the cert petition. Thanks to HowAppealing for this news.