Gravitational ultrarelativistic spin-orbit interaction and the weak equivalence principle

It is shown that the gravitational ultrarelativistic spin-orbit interaction violates the weak equivalence principle in the traditional sense. This fact is a direct consequence of the Mathisson-Papapetrou equations in the frame of reference comoving with a spinning test body. The widely held assumption that the deviation of a spinning test body from a geodesic trajectory is caused by tidal forces is not correct.