Newton's Third Law is inviolate, it's another way of saying momentum (both linear and angular) is always and everywhere conserved, no exceptions. This follows from Noether's Theorem, which says that every symmetry in nature leads to a conservation Law. The symmetry that any behavior of nature is the same over any interval of time leads to conservation of energy; that it's the same in any location in space leads to conservation of linear momentum; and that it's the same however things are oriented in space leads to conservation of angular momentum. So the ONLY way, and NO exceptions, to accelerate a spaceship or any other massive object, is to push or eject or shoot or exhaust something in the other direction. It can be as simple as getting a rowboat across a pond by throwing rocks out the back end, or it can be done (very poorly) by shooting radiation out the back. That this is a very poor method can be seen by looking at the relativistic energy-momentum-mass equation, E^2 = p^2*c^2 + m^2*c^4. For radiation m = 0; taking the square root and diving by c gives p = E/c. So you can generate a HUGE amount of radiant energy and blast it out the rear, but the momentum that's transferred to the ship is all that energy divided by the speed of light, which is a REALLY BIG number. In other words, many megawatts of radiant power provide at most a teeny-weeny bit of momentum. In short, the EM drive or anything remotely like it will NOT work.