This paper investigates the rise of foreign investment screening mechanisms (ISM) over the last two decades.  Originally conceived as a policy to regulate the foreign control of sensitive industries for national security reasons, ISMs have proliferated across broader sectors of national economies.  We formally analyze the sectoral-level choice of ISM adoption in a model that emphasizes norms within networks of international relations as the driving force behind the spread of ISMs.  We argue that as more economies adopt ISMs across sectors of the economy, the cost of violating norms of economic openness decreases for the other networked economies, and ISM adoption spreads.   We then empirically scrutinize the role of network effects using a unique country-sector-level panel data set on ISM adoption.  We conclude that network effects explain ISM adoption, and, examining a broad variety of network linkages that economic linkages are more important than political and institutional linkages.