The article proceeds by first describing the relationship between law and legitimacy as suggested by U.S. counterinsurgency doctrine. The rule of law and legitimacy are not the same thing, though, and so the second part of the article addresses how the “rule of law” can actually build legitimacy. Because building legitimacy is not the only way law is used in counterinsurgency, a complete answer to the law/legitimacy question requires an understanding of how law is actually used in counterinsurgency. That question is addressed in the third part of the article, describing the four ways law is used in counterinsurgency and how those various uses relate to legitimacy and thereby to the authority of the law. A complete understanding of how law is used by counterinsurgents reveals that the many uses of law in counterinsurgency fall along a continuum of legitimacy. Keeping that continuum in mind has implications for practice, which are covered in the fourth part of the article, followed by a brief conclusion.