Space deployments are banned by the Outer Space Treaty [1]. Slide 3 mentions Fractional Orbital Bombardment System (FOBS) which was not banned by the Outer Space Treaty but subsequently by SALT II. Interestingly enough the US never ratified SALT II [2].

[1] https://en.wikipedia.org/wiki/Outer_Space_Treaty

[2] https://en.wikipedia.org/wiki/Fractional_Orbital_Bombardment...