For all Poincare invariant Lagrangians of the form L = f(F-mu nu), in
three Euclidean dimensions, where f is any invariant function of a non
-compact U(1) field strength F-mu nu, we find that the only continuum
limit (described by just such a gauge field) is that of free field the
ory: First we approximate a gauge invariant version of Wilson's renorm
alization group by neglecting all higher derivative terms similar to p
artial derivative(n) F in L, but allowing for a general non-vanishing
anomalous dimension. Then we prove analytically that the resulting flo
w equation has only one acceptable fixed point: the Gaussian fixed poi
nt. The possible relevance to high-T-c superconductivity is briefly di
scussed.