First, thanks for another really excellent essay on this most important topic from this author.

There is morality, and there are laws. People are put in prison--and in some cases "euthanized"--for breaking laws: the governance of society is a material necessity that our propensity to live together in groups foists upon us human beings.

(Just*) laws are based on 'harm'. Harms are identified and actions generating harms are proscribed. "Morality" need not enter into it, especially as an a priori determinant of laws.

'Free will' need not enter into it, either. The motivations and intentions of someone who undertakes some action that is illegal might possibly be taken into account in determining punishment, but the law itself and the process undertaken to ascertain guilt or innocence are material matters concerning 'harm'. Harm can be immaterial, as in causing emotional or psychological harm, but it can only result from persons acting (including 'speech acts') within material existence.

*I have demonstrated that 'justice' not only can be, but must be wholly contained within material existence. If curious, "Can't Get Any Simpler" is a "2 min read" here in Medium, with links to more on the topic. (Nothing I publish here is behind the paywall.)