It is up to both. Because of the way things are structured, trump would need to get a super majority in both Denmark, and Greenland. Basically, he would have to come up with such an overwhelming amount of money to the Greenlanders, that every last one of them felt like they won the lottery, and come up with such a large amount of money to the Danes, that every last one of them would see a huge drop in their taxes. It is a number in the trillions, and it cannot be paid in US Dollars. The US Dollar is printable by the US Government, so no one is accepting it for something like this. There is only one other entity in the world that can produce that kind of money. So in effect, we would need the EU's approval. Actually, Greenland is not part of the EU, so not because of that, but to get enough money to fund this purchase. I think the EU will demand the right to tax American citizens to approve it. And forget about any tariffs. It would require some huge sacrifices in both money and sovereignty.
