The legal and political ramifications of the collision with Andromeda will be tremendous. Once-stable star empires will find their territory being violated by other star empires' actual stars
. How do the lawyers sort that out? Is the empire whose stars have the higher average velocity relative to the average of the two galaxies considered the interloper? Will we have to define inter-stellar "right of way" to resolve disputes? Will the interloping star systems have to pay damages for orbital disruptions? It will be chaos.