What has to happen for the U.S. to gain sovereignty over Greenland?
First step: Congress. A joint resolution will work; a treaty isn’t necessary. But you need Congress both to get the money and to bring the territory into the Union.1
Second: Simultaneous negotiations with Greenland and Denmark. To an extent, the Danish negotiations would be a sideshow, since they aren’t the ultimate decision-makers. But the Danish government could throw a wrench into the operation. Without their consent, Greenland would need to declare independence and then sign over its sovereignty to the United States. Under Danish law, that requires a joint referendum in both Greenland and the United States. If the plan is to have Greenland sign declare independence and then join the United States in a simultaneous vote, it will require planning.
Third: A serious monetary offer to Greenlandic citizens rather than the government. The legislators who will need to authorize the a referendum on the offer will know that they stand to receive $400,000 or $800,000 or whatever it is should it pass. In the words of James Bosworth, “There are not a lot of legislators on the planet who would remain impartial in the face of that sort of incentive.”2
Fourth: The fine print. The Covenant between the Commonwealth of the Northern Marianas Islands (CNMI) and the United States is extremely detailed. It gives the CNMI a level of autonomy much greater than any American state, and the courts have upheld it. The level of detail for a Greenlandic covenant should be at least as high. And the Americans should be willing to be innovative. Lay out the conditions to under which the Commonwealth of Greenland can apply to Congress for statehood? Okay. Lay out the conditions under which the Commonwealth of Greenland can secede, a la the Commonwealth of the Philippines? Not a problem. Exempt the territory from the Jones Act? Utterly reasonable. Anything else the Greenlandics ask about? Work it out! If the negotiation wants to succeed, the only U.S. red lines should be on defense, mineral rights, and regulation.
All of this would be complicated, save possibly step (3). It would take a long time, and the U.S. negotiators would have to bring their A-game.
I wish I could say that I was confident that the Trump Administration could pull this off, but I would like to be pleasantly surprised.
It is true that Congress didn’t ratify the 1900 cession by the Samoan high chiefs of what became American Samoa until 1929. President McKinley just agreed to the cession and handed the islands over to the Department of the Navy to run. But the U.S. Senate did ratify the Tripartite Convention of 1899, in which the U.K. declared that it “renounces in favor of the United States of America all her rights and claims over and in respect to the Island of Tutuila and all other islands of the Samoan group east of Longitude 171° west of Greenwich.” The implication is that in the absence of a joint resolution, Congress would demand some legal instrument ratifying American claims.
It is worth pointing out that as American citizens, Greenlandics will be entitled to Social Security in addition to their Greenlandic pension benefits.