system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] Doesn't the Federation have laws against genocide?

In the TNG episode "The Survivors" we meet a Douwd who had been posing as a human. At the end we find out that in a fit of hatred and temporary insanity he wiped out the entire Husnock race. 
Once Picard realizes the  truth he tells him. 

"We are not qualified to be your judges. We have no law to fit your crime. You're free to return to the planet, and to make Rishon live again." 

Yes, being a judge over such a trial would be a heavy burden, no doubt on that. And yes, having that responsibility would be too much for anyone.  But he also says they have no laws to fit that crime. Wouldn't it fall under laws against Genocide? Because that is what it was.
gpt
They probably do, and the punishment is probably death but the perpetrator here was a godlike being. The Federation, never mind the Enterprise on its own, might not have the ability to kill him, and worse, might trigger another genocide in the process of trying - he had already demonstrated that he might lash out under extreme stress. Picard must have decided warning Federation ships away and hoping the Douwd stayed put on the planet was the best course of action.