I’d like to know what has changed. My assumption is that it has always been legal given it was done for reasonable reasons (national security, etc). Are they claiming that now the president can kill anyone they wish with no reason whatsoever? Has this wholly removed the fourth section of Article II?

The President, Vice President and all civil Officers of the United States, shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors.