The Outer Space Treaty of 1967 - yes there really is one - theoretically precludes it, but how much you wanna bet we'll see an arms race in space soon? I think there's money to be made in laser beams, people.
Through a formal proposal at a disarmament discussion, though, the Russians and Chinese have challenged the U.S. not to weaponize space.
Does this mean the Alan Parsons Project is finished? I hope not.