Glashow and Cohen make the interesting observation that certain proper subgroups of the Lorentz group like HOM(2) or SIM(2) can explain many results of special relativity like time dilation, relativistic velocity addition and a maximal isotropic speed of light. We show here that such SIM(2) and HOM(2) based VSR theories predict an incorrect value for the Thomas precession and are therefore ruled out by observations. In VSR theories the spin-orbital coupling in atoms turn out to be too large by

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... factor of 2. The Thomas-BMT equation derived from VSR predicts a precession of electrons and muons in storage rings which is too large by a factor of 10^3. VSR theories are therefore ruled out by observations.