A 1/B3 scaling law is derived for anomalous diffusion produced by the dissipative trapped-ion instability in axisymmetric toroidal plasmas with shear. The theory presented by the authors helps to explain why transport of this type has not been detected in the PLT heating experiment, so far. In addition, it is shown that the Kadomtsev-Pogutse diffusion formula, will contradict the trapped-fluid equations from which it was deduced, provided that the necessary boundary conditions are observed.