  We show a transitivity property of nonlocal correlations: There exist
tripartite nonsignaling correlations of which the bipartite marginals between A
and B as well as B and C are nonlocal and any tripartite nonsignaling system
between A, B, and C consistent with them must be such that the bipartite
marginal between A and C is also nonlocal. This property represents a step
towards ruling out certain alternative models for the explanation of quantum
correlations such as hidden communication at finite speed. Whereas it is not
possible to rule out this model experimentally, it is the goal of our approach
to demonstrate this explanation to be logically inconsistent: either the
communication cannot remain hidden, or its speed has to be infinite. The
existence of a three-party system that is pairwise nonlocal is of independent
interest in the light of the monogamy property of nonlocality.
