Scientifically speaking other galaxies have the same laws of Physics as our galaxy.
This is a basic axiom of science. There has been discussion that some values of constants may change over time (although I think this has been rejected based on observation), the assumption is that the laws of Physics work the same throughout the Universe.
Of course, we have never been to another galaxy... so we have no direct experience of how things work in other galaxies. However, we can make observations, we can see how Galaxies move, and we can look at the electromagnetic radiation that comes from Galaxies. We have no reason to believe that other galaxies don't follow the same laws.