I’m not a lawyer but I think that falls under the laws governing voluntary “mutual combat”
I think the laws vary from state to state but they usually refer to more spontaneous fighting than a planned fight. It also might fall under laws the laws and regulations that govern boxing in your state. Honestly, I don’t know. I probably shouldn’t have answered this question. Consult a lawyer.

A lawyer WOULD be the one to ask. But IMHO, if your opponent DIES due to your punches, I can see that becoming a wrongful death civil lawsuit. You’re not supposed to die, even in a boxing match.

In English criminal law there is a defence specifically arranged for violent sport related deaths which, if applied correctly, can make a person not guilty of murder/manslaughter. This defence cannot however be used should excessive force be used in what was intended to be a simple sparring session (assuming the court knows this to be so).
In English civil law alot more variables would be considered but generally I doubt the defendant would be found liable if the victims signature were written on a contract and it was a known fact that he entered the match aware that he may be fatally harmed or killed.
As I say, this is English law so if you live elsewhere it may not prove to be much use but you may be able to find similarities in the law of the country you live in. It is a pretty reasonable law afterall.

Ray ‘Boom Boom’ Mancini didn’t face charges after Duk Koo Kim died of a brain injury after their bout. But that was a professional boxing match, I’m not sure about a pick-up match, but I’ll bet the person who caused the injury would be liable.

@Nially_Bob I think there’s a (bad) slogan for the British courts in there: “There’s Never Been a Better Time to Try English Law. It’s Pretty Reasonable, After All.”

As long as the fight is sanctioned there would be no legal action. If you hold an unsanctioned fight (underground) then manslaughter would be a highly likely outcome if a fighter died. Even when death occurs during a sparring match it is unlikely there would be any legal action taken due to the liability wavers the gym/fighters are covered by.

@drClaw How would one go about sanctioning these fights?

You would have to first find out if your area even allows fights. There are a lot of places that just won’t allow it. If they do allow fights then the fights would be governed by a sanctioning body. You would need to find these things out then submit a request to throw a fight through the sanctioning body.

The other thing to think about is the level of the fighters, the sanctioning body will only concern themselves with pro fighters (are they getting paid). If you are planning on throwing an amateur fight then your two options are to come up with your own liability waivers and find a local gymnasium large enough to house the fights or just go underground and be careful about who knows your running the show.

This was helpful, thanks all.

@lillycoyote Hahahaha, I feel people could appreciate the modesty (or is “pretty reasonable” a stretch?)