We study the regulation of a utility firm which is active in a competitive unregulated sector as well. If the firm jointly operates its activities in the two markets, it enjoys economies of scope, whose size is the firm’s private information and is unknown to the regulator and the rival firms....

We analyze the design of optimal regulation of a domestic monopolist that also competes in an unregulated foreign market. We show how foreign activities by the regulated firm affect domestic regulation, consumers’ surplus and firm’s profits. Although expansion in unregulated foreign markets...