The non-existence of free will has no direct policy implication. Since people are deterministic, the knowledge of punishments would create different behaviors.
https://www.orlandocriminaldefenseattorneyblog.com/2016/01/f...
If a criminal has no free will, then they are not responsible for their actions since responsibility is dependent on moral agency. I disagree with that author's conclusion though, that you have to let every criminal go. I think that when someone is apprehended and determined to have committed the crime the decision to be made now comes from a different perspective. What treatment of this person will produce the best (or least bad) outcome for society on the whole? In one case that could mean letting the person go if every indication is that they will not commit another crime regardless of any punishment. In another case it could be locking them up and never letting them out, even on a first offence, if it is very likely that they will commit serious crimes if freed.
Of course there are still discussions to be had weighing the impact of the sentencing decision on the victim, the perpetrator, and the rest of society. There's also how much trust to place in the scientific models of likelihood for recidivism. But accepting that people have no moral agency undercuts the most basic premise of laws and the justice system.
A deterministic universe does not mean people do not have moral agency. It just means some people are predetermined to behave immorally. That does not mean we should not do what we can to prevent that behavior.