In fact, the Outer Space Treaty of 1967 bans militarization. Potential adversaries of the US, and even its allies, are so far behind that these countries are very interested in maintaining the treaty. Europe and the rest of the world want a strong reaffirmation of the Treaty and the US is unilaterally trying to derail it. Termination of the treaty would mean that the US could develop satellite weapons, put offensive weapons in space. It would probably mean using nuclear power in space. All of this leads to some very dangerous scenarios, including destruction of the species.