  We provide a method of designing protocols for implementing multipartite
quantum measurements when the parties are restricted to local operations and
classical communication (LOCC). For each finite integer number of rounds, $r$,
the method succeeds in every case for which an $r$-round protocol exists for
the measurement under consideration, and failure of the method has the
immediate implication that the measurement under consideration cannot be
implemented by LOCC no matter how many rounds of communication are allowed,
including when the number of rounds is allowed to be infinite. It turns out
that this method shows---often with relative ease---the impossibility by LOCC
for a number of examples, including cases where this was not previously known,
as well as the example that first demonstrated what has famously become known
as nonlocality without entanglement.
