This paper constructs agreement specific instruments in order to estimate the effect of membership in a regional cooperation agreement (RCA) on institutional change. For a sample of 144 emerging and developing economies, the results show that membership in a RCA explains a significant part of the cross country variation in institutional reforms. EU and NATO-related agreements are an important reason why emerging markets in Eastern Europe and Central Asia have been better reformers despite their socialistic heritage. RCAs are a main factor why African economies are still doing very poorly in terms of institutional reforms. I show that the construction of the RCA and the willingness delegate sovereignty is behind the effect on institutions and is an important transmission channel of how historical experience are shaping current institutions.