Cislunar space, the region between Earth and the Moon's orbit, is now included in US military planning scenarios. ^[4] That planning coexists with the 1967 Outer Space Treaty, which the US agreed to and which bans the building of lunar military bases and any weapons testing or military exercises on the Moon. ^[1] Under US law the definition of cislunar is vague, with uncertainty over whether it includes the Moon's surface itself. ^[2] Aaron Brynildson, a space law professor at the University of Mississippi, told Defense One the US needs better capabilities in cislunar space to ensure China complies with its obligations and does not militarize the Moon. ^[3]