Amid Donald Trump’s continued insistence on annexing Greenland, several Democrats have raised the possibility of invoking the 25th Amendment.

Since returning to office last year, the president has repeatedly spoken about taking control of the Danish territory, arguing that the United States “needs” to own Greenland immediately for reasons tied to national security.

The proposal has drawn sharp criticism from European leaders. In response, Trump has threatened to impose a ten-percent tariff on eight European countries beginning in February. According to the administration, those tariffs would increase to 25 percent by June if negotiations fail to secure what Trump has described as the “complete and total purchase of Greenland.”