We all complain about judicial activism, whether it's by the Supreme Court of an Appeals Court. What happened here is no different. The law mandates a minimum sentence. The Supreme Court has upheld minimum sentences. For the district court to decide that they weren't bound by the law is judicial activism, no more and no less. It's their job to uphold the law, not make it.
Too bad they haven't upheld other laws. The whole judicial system is arbitrary and capricious. They enforce the laws they want enforced, and refuse to enforce the ones they don't like. We've seen it time and again with this Administration. They have repeatedly refused to follow the orders of the courts if they don't agree, and nothing has been done to them.