  We show that any two different unitary operations acting on an arbitrary
multipartite quantum system can be perfectly distinguishable by local
operations and classical communication when a finite number of runs is allowed.
We then directly extend this result into the case when the number of unitary
operations to be discriminated is more than two. Intuitively, our result means
that the lost identity of a nonlocal (entangled) unitary operation can be
recovered locally, without any use of entanglement or joint quantum operations.
