  Scattering amplitudes in three-dimensional N=6 Chern-Simons theory are shown
to be non-invariant with respect to the free representation of the osp(6|4)
symmetry generators. At tree and one-loop level these "anomalous" terms occur
only for non-generic, singular configurations of the external momenta and can
be used to determine the form of the amplitudes. In particular we show that the
symmetries predict that the one-loop six-point amplitude is non-vanishing and
confirm this by means of an explicit calculation using generalized unitarity
methods. We comment on the implications of this finding for any putative Wilson
loop/amplitude duality in N=6 Chern-Simons theory.
