Immigration law is necessarily a comparative legal practice in at least three aspects: (i) comparing a would-be immigrant’s criminal history to the destination state’s criminal laws; (ii) comparing an immigrant’s diplomas and education to the destination state’s educational system; and (iii) comparing immigrants’ marriages and intimate relationships to domestic family law regimes. For all of these questions, the methodological dilemmas of comparative law are repeated within immigration law. This article is an overview of all the comparative methods used in North American immigration laws since the 1880s, for evaluating criminal records and intimate partnerships. The methods range from plain translations to complex systemic comparisons. Over the last 130 years, almost all methods had some, either good faith or strategic use; with the biggest transformations happening in the comparison of marriages. Effectively, private international law has been replaced by a separate “immigration marriage law,” which has globalized at astonishing speed.