There is the Outer Space Treaty (1967), which forbids placing "nuclear weapons or other weapons of mass destruction in orbit or on celestial bodies or station them in outer space in any other manner", but you can get around that by saying that it's just a conventional weapon, not nuclear or WMD. If it's for space to space combat, you could say that any weapon is potentially a WMD due to the Kessler potential, but if its space to ground, like an orbital missile platform or something, you are technically in the clear.
I'm guessing it doesn't ban weapons in space completely because of things like the survival guns on Soyuz (if they still fly them), used for defending yourself against wild animals in the event that you land in a forest or similar. "No weapons in space" would ban that as well, but I think it's reasonable to have a survival kit, just in case
I'm guessing it doesn't ban weapons in space completely because of things like the survival guns on Soyuz (if they still fly them), used for defending yourself against wild animals in the event that you land in a forest or similar. "No weapons in space" would ban that as well, but I think it's reasonable to have a survival kit, just in case