Since the Batarians withdrew from Citadel space, I think the events of Arrival are strictly between the Systems Alliance and the Batarian Hegemony, so Arcturus Station would be the most logical place to hold a trial. I'm sure the other council races will chime in with condemnation, but by their own rules it's none of their business.
As for the human/reaper thing...well at some point the stakes for a hero have to become personal, and what's more personal than your entire species being liquefied? Even so, it's not like the reapers plan to make baby human reapers and then skedaddle back into dark space; they're going to wipe out all of the other space faring species and fix the damn keepers so they don't have to walk back next time too. So like I said, I can really see a "victorious" ending where Earth is still lost.