Can Magnetic Charge and Quantum Mechanics Co-exist ?

It is proven that if more than a single magnetic charge exists it is impossible to define a proper quantum mechanical angular momentum operator for an electrically charged particle in the field of the magnetic charges. Assuming that quantum mechanics is correct we conclude that free magnetic charges (i.e. magnetic charges with a Coulomb-like magnetic field) can not exist. The only apparent way to avoid this conclusion is if magnetic charges do exist, they must be permanently confined in monopole anti-monopole pairs, much in the same way quarks are thought to be confined.