A galaxy 16 billion light years away is moving away from us faster than light, but that distant galaxy isn’t defying relativity. After all, from that distant galaxy’s perspective we are moving away from it faster than light, speed being relative and all. The key point to remember is that this relative motion is due to cosmic expansion, not galactic motion. Relativity requires that nothing can move through space faster than light. It places no constraint on the expansion of space itself.