In this paper, we re-examine the classical questions of implementation theory
under complete information in a setting where coalitions are fundamental be-
havioral units, and the outcomes of their interactions are predicted by applying
the solution concept of the core. The planner’s exercise includes designing a
code of rights that speci…es the collection of coalitions having the right to block
one outcome by moving to another. A code of individual rights is a code of
rights in which only unit coalitions may have blocking powers. We provide the
necessary and sufficient conditions for implementation (under core equilibria)
by codes of rights, as well as by codes of individual rights. We also show that
these two modes of implementation are not equivalent. The results are robust
and extend to alternative notions of core, such as an externally stable core.
Therefore, coalitions are shown to bring value added to institutional design.
The characterization results address the limitations that restrict the relevance
of the existing implementation theory.