  Non-locality is the phenomenon of observing strong correlations among the
outcomes of local measurements of a multipartite physical system. No-signaling
boxes are the abstract objects for studying non-locality, and wirings are local
operations on the space of no-signaling boxes. This means that, no matter how
non-local the nature is, the set of physical non-local correlations must be
closed under wirings. Then, one approach to identify the non-locality of nature
is to characterize closed sets of non-local correlations. Although non-trivial
examples of wirings of no-signaling boxes are known, there is no systematic way
to study wirings. In particular, given a set of no-signaling boxes, we do not
know a general method to prove that it is closed under wirings. In this paper,
we propose the first general method to construct such closed sets of non-local
correlations. We show that a well-known measure of correlation, called maximal
correlation, when appropriately defined for non-local correlations, is
monotonically decreasing under wirings.
  This establishes a conjecture about the impossibility of simulating isotropic
boxes from each other, implying the existence of a continuum of closed sets of
non-local boxes under wirings. To prove our main result, we introduce some
mathematical tools that may be of independent interest: we define a notion of
maximal correlation ribbon as a generalization of maximal correlation, and
provide a connection between it and a known object called hypercontractivity
ribbon; we show that these two ribbons are monotone under wirings too.
