Extraterritorial maritime interdiction is a common tactic used by destination states to keep unwanted migrants from reaching their borders.

Population policies aim to alter demographic behavior, but their impact can depend on their origins.

We analyze these origins using an innovative method—plagiarism detection software—to determine when countries copy policy text from one another or from international sources, focusing on fertility and refugee policies in sub-Saharan African countries. We find that countries directly copy 8% of text on average, but that refugee policies copy significantly more text than fertility policies. We also find that poorer countries borrow more text, and that other countries’ policies are preferred to international templates (such as UN conference programs of action, or international conventions). We find no effect on copying of countries’ connections through geographic proximity, regional organizations, or trade. We interpret these findings in terms of the differing strength of international regimes around refugee and population law, as well as the varied capacity of countries to produce policy, and discuss their implications for policy impacts.