Unilateral migration policies impose externalities on other countries. In order to try to internalize these externalities, countries sign bilateral migration agreements. One element of these agreements is the emphasis on enforcing migration policies: immigrant-receiving countries agree to allow more immigrants from their emigrant sending partner if they cooperate in enforcing their migration policy at the border. I present a simple theoretical model that justifies this behavior by combining a two country, two-good classical Ricardian model with welfare maximizing governments. These governments establish migration quotas that need to be enforced at a cost, modeled according to Ethier (1986b). I prove that unilateral migration policies are inefficient. Both countries can improve welfare by exchanging a more “generous” migration quota or terms of trade advantages for expenditure on enforcement policy. Contrary to what could be expected, this result does not depend on the enforcement technology that both countries employ. The Ricardian assumption is not crucial either and a generalization of the model is introduced.

JEL Classification: F22
Keywords: international migration, cooperation, migration policy