  We prove that N=2 theories that arise by taking n free hypermultiplets and
gauging a subgroup of Sp(n), the non-R global symmetry of the free theory, have
a remaining global symmetry which is a direct sum of unitary, symplectic, and
special orthogonal factors. This implies that theories that have SU(N) but not
U(N) global symmetries, such as Gaiotto's T_N theories, are not likely to arise
as IR fixed points of RG flows from weakly coupled N=2 gauge theories.
