The First Interdimensional Lawsuit (or justification for war)
Apparently we're in a mirror universe where humans are the worst. I try and try to get the members of Starfleet that I serve with to act reasonably, and obey interstellar law, and what thanks do I get? The spore drive goes bonkers and we end up in a universe where there is no United Federation of Planets, rather there is a Terran Empire! And these Terrans are monsters. I stopped keeping track of various war crimes and crimes against the galaxy because apparently the only crime in this place is to let yourself be seen as weak. However, now that we (1) know multiverses are a thing, and (2) figured out a way home, there is something that I want to address.
The spore power plant at the center of the Emporer's ship likely violates what I am now going to call "Interdimensional Law." I'm not really sure what we can do about this, but I wanted to keep a record anyway. The Emporor was operating the spore drive at a dangerous rate that is unsustainable. Not only would it eliminate its own supply of mycelium spores, but that would affect all spores across the multiverse (you see, it was the spore drive that allowed us to get here in the first place. It transcends... you know, I'll just let you read the science nerd logs for that. But, just because they are polluting or wasting a resource in one dimension does not mean that we have to sit idly by and take it.
Trans-Boundary Pollution: There is still caselaw on the books that stays that a "State owes at all times a duty to protect other States against injurious acts by individuals from within its jurisdiction."1 That case even cites older cases that hold that a State can hold another State liable for "actual encroachment which might prejudice the natural use of the territory and free movement of its inhabitants."2
Ecosystem Change: There are even interstellar bodies that are in existence today that stem from much older international bodies responsible for climate change. Hundreds of years ago, the governments of Earth created the United Nations Framework Convention on Climate Change in order to get everyone on board with addressing sea-level rise, and carbon in the atmosphere. Today it's the United Federation of Planets Convention on Galactic Sustainability. The fact that it has lasted this long, and is this widespread indicates that not using up a natural resource is an interdimensional jus cogens, and would apply to the Terran Empire, whether they believe it or not.
I don't believe that we'd be successful in getting the Emperor to submit to arbitration, but this may be a proper justification for war. As long as they keep abusing the spore network every other universe in existence is in peril!
1 Trail Smelter Case (United States v. Canada), Arbitral Tribunal, 3 U.N. Rep. Int'l Arb. Awards (1941).↩