I mean, let’s be honest: People do crimes even when they have no material need to do so, so you will always need some form of law enforcement, how should a solarpunk society handle this?
The same is true for a military: As long as there is no world peace or some magical way to shut the outside world out, and as long as other societies exist somewhere nearby (and in today’s world this means somewhere on the same planet), a society needs the means to defend itself… what would this look like?
Community Volunteers that switch out every 2 weeks to prevent getting used to that much power, they carry only nonlethals and de-escalate. Punishment could be a community vote for exile, seizure of property, etc. (for law enforcement)
And the military should be several decentralized militias working together. The Afghanistani rebels can fend off huge empires because theyre decentralized.