Donald Trump can be accused of many things, and very serious ones. But not to blow up an international law that, historically, the great powers have always ignored when it has been convenient for them. In fact, what we call international law has never been more than a concession of the strongest and, secondarily, an optional resource to which the strongest have resorted when it has been easy and convenient for them.
The United States had the approval of the UN to invade Kuwait in 1991. In 2003 it did not obtain it to invade Iraq, and the war (accompanied by the great hoax of weapons of mass destruction, in which Tony Blair and José María Aznar cooperated) happened anyway. The Soviet Union appealed to the Warsaw Pact to justify the invasion of several European countries in its orbit (Hungary in 1956, Czechoslovakia in 1968), but in 1979 it invaded Afghanistan simply because it believed it appropriate.