Basically, I have a sci-fi world with intelligent animals. The story is that long after humans disappeared from the Earth, animals eventually become intelligent and made their own society to replace them. One major development in their history is that predators and prey agreed to live in harmony, signing treaties, making laws, and generally working very hard to ensure lasting peace between natural enemies.
One aspect of this is of course prosecuting animals that engage in predation. The way criminal trials work in this world is that every animal has the right to be tried by members of their own species or taxonomic group, who are also responsible for carrying out sentencing. Each animal has a taxonomic government to answer to, so if you're a cat you are under the jurisdiction of the Feline government, mouse, Rodent government, bird, Avian government, etc. Each animal follows the same basic laws and regulations that all taxonomic governments agree on, things like prohibiting predation is one of these, but each government can also pass taxon-specific legislation, and are also able to determine criminal penalties independently.
The Felines only had their revolution a few years ago, when they overthrew their old kingdom which was very pro-predation, and made a republic that has signed the Interspecies Peace Agreement and is therefore very anti-predation. Because it's so recent, the Felines also have the harshest punishments for a predation conviction made after the revolution. One count of first degree predation (when you personally kill then eat an animal) is an automatic life in prison without parole, the same penalty as "regular" murder without eating the victim, two or more counts is life in prison unless the prosecution requests for the death penalty at the start of trial and this is authorized by both the judge and the Feline Ministry of Security. Generally, courts stop at two predation convictions even if it's obvious that the defendant committed more, since that's enough to either put them away forever with no chance of parole, or kill them. Second degree predation, AKA simple predation, where you eat already dead animals that someone else killed, is treated much less harshly and sentencing options only has fixed term imprisonment possibly with parole, though with restrictions afterward like you can't work in the government or security-critical industries unless the court lifts those restrictions on a case by case basis. The ISPA lists execution after being convicted beyond a reasonable doubt of a crime that causes the death of two or more other animals as the only exception to the no killing rule, and it can only be done by members of the same species or taxonomic entity, and is also subject to oversight and can even be blocked outright by other ISPA members through the ISPA Inter-Taxon Court, so they also do not have full autonomy on who they can execute, and taxa that have the death penalty much also must make their execution methods (which are mandated to always prioritize minimizing suffering), judicial procedures, and statistics public.
They do also use the threat of execution as a way of getting information about a predation case though. If they catch a Feline who is apart of a predation ring, it's better than nothing but they'd obviously much rather take down the leader and the entire organization. The Feline Ministry of Security can basically tell the accused "Look, your trial date has been set, the prosecution has requested authorization to use the death penalty from us, and you know what evidence they have on you. We're still trying to decide if we want to grant that request. It's up to you and we can't force you to give us any information, but is there anything you want to tell us about your organization or do you want to gamble with whether you'll be found guilty or not?" Funnily enough most of these cats don't care that they're killing sapient prey animals that have lives and families and stories, but break real fast when it's their own life on the line.
The Felines (and any ISPA member for that matter) can also arrest other species if they commit a crime on their territory or against a their own animals, but within the Interspecies Peace Agreement member species, animals have the right to stand trial and receive sentencing by their own species or taxon, so most they can do is investigate the crime, form a case with evidence, and then extradite the defendant back and forward their findings to the government that actually has jurisdiction. Most they can do to a non-Feline is detain them, extradite, and then ban them from Feline territory. However, any ISPA non-signatories, AKA predators that are actually predators and eat prey, who engage in predation, either against any ISPA member species anywhere in the world, or on ISPA territory against any animal; are not granted this right (obviously, since if you extradited them back to their own territory they'd be home free). So if you eat a cat or eat a mouse or bird or any other animal on Feline territory, you are dealt with just like any predatory cat by the Feline government regardless of what the laws by your own taxonomic government is.
I should also add that every animal is intelligent/sapient in this world. So predation really would be like murder. No copouts like eating fish or whatever.
Even in universe this is quite controversial even among prey species so I'm not trying to claim that this is the ideal state of the law, but I'm more trying to make sure if this makes sense or not. I also know that they will almost certainly have very different morals and ethics for humans, but then again I'm writing this story for humans so not sure how relevant that actually is. Is the motivation of having a death penalty despite not even allowing animals to eat meat a realistic one?