He has a right of free speech. He doesn't have a right to *be* in this country. He should have been arrested or captured the moment he stepped off the airplane. Even if he weren't a criminal and a terrorist, he'd still not have the right to be here. Even as a diplomat/leader going to speak at the UN, he could have been restricted to his hotel room, the airport and the UN, and been required to travel directly between them.
Where in the U.S. Constitution does it guarentee a foreign leader the right to free speech?