This article provides the personal perspectives of US military operational attorneys and analyzes three significant challenges in applying international humanitarian law (IHL) to modern military space operations: the lack of clear standards for assessing when IHL rules govern particular military activities in outer space; the challenges of effectively distinguishing between civilian objects and military objectives when targeting space systems; and the difficulties of applying IHL rules of proportionality when attacking space systems. To address these challenges, the article argues that States should take steps to develop non-binding norms for military space operations that contribute to broader understanding of States’ views on how IHL applies in space.