  We examine problems of ``intermediated implementation,'' in which a single
principal can only regulate limited aspects of the consumption bundles traded
between intermediaries and agents with hidden characteristics. An example is
sales, in which retailers offer menus of consumption bundles to customers with
hidden tastes, whereas a manufacturer with a potentially different goal from
retailers' is limited to regulating sold consumption goods but not retail
prices by legal barriers. We study how the principal can implement through
intermediaries any social choice rule that is incentive compatible and
individually rational for agents. We demonstrate the effectiveness of per-unit
fee schedules and distribution regulations, which hinges on whether
intermediaries have private or interdependent values. We give further
applications to healthcare regulation and income redistribution.
