LAST week Bill Clinton did something indefensible in international law. He visited a country without being invited, and against the wishes of its government and president. Worse, while there, he issued a call to its people to overthrow the regime. The country was Yugoslavia, the president, Slobodan Milosevic. But didn't Clinton visit Kosovo? He did, but according to the agreement in June to end Yugoslavia's aerial bombing, Kosovo stays a part of the country, albeit an autonomous one. So was Clinton thumbing his nose at international law and proclaiming US overlordship of the world? The answer is startlingly different.