Too many people see only a libertine right in the 2nd clause of the 2nd amendment and not the responsibility of the 1st clause.
The law should mandate safety, storage, usage, and citizenship training for armed citizens. Based on type of gun this should take place with either a local police force or the National Guard, with an exception carved out for single shot hunting rifles. In person training should be at least once or twice a year, for a maximum of a day, at times assigned sufficiently in advance to not disrupt lives.
This regulated militia would be attached to the force they have trained with, but shall not be called up outside of mandatory training without adequate compensation.
Failure to train, without good reason, would be a felony with consequent loss of firearms rights.