Abstract: Commissioner Meissner has emphasized for us the importance of naturalization and the need to "put the N back into INS." The present Article aims toward an analogous goal: putting the "n" back into immigration law scholarship. It will not treat the requirements for naturalization as straight-forward, which in an academic context could mean undeserving of serious attention. Instead, it will inquire into their justifiability. By justifiability, I mean political justifiability, measured against the political principles applied in other legal contexts in the United States. Occasional discussions of the constitutionality of naturalization criteria dwell on the question whether congressional power over naturalization is "plenary" in the sense of being subject to no constitutional constraints, subject only to a rationality requirement, or immunized from judicial review. This Article will not address that issue of positive constitutional law, and will advert to constitutional doctrine only as one source of political principles applied in the United States. Although the inquiry begins somewhat abstractly, the focus will be entirely on the U.S. context, and (accordingly) the naturalization of aliens who have already been admitted as permanent residents. In some cases, parallel arguments might be made about the naturalization policies of other nations, but I have not attempted to keep track of the degree of generality of the arguments. For the United States, I will identify four simple normative models of naturalization of resident aliens. Each of these models comes with its own set of constraints on the justifiability of naturalization ...