Most states have 'law laws' from their legislative branch that give the executive branch (the governor and state agencies) the power to create administrative laws as you said. So, for example, the state legislature doesn't determine what the speed limit will be for every road in the state, but it gives the executive's department of transportation the authority to make those determinations. And it is enforced by the police and judicial branch and you can be fined and/or imprisoned for breaking a merely administrative determination of a speed limit for a particular road.
And most states give the executive branch the authority to come up with all sorts of ad hoc rulings during times of emergencies including health emergencies. In NJ, after weeks of warnings, citizens were getting citations for breaking the rules the governor made. Citations from the police. Businesses that opened when they weren't supposed to were getting citations. Courts were ordering them to close based on the governor's rules, and not any from the legislature, except for the fact the legislature gave NJ governors the powers to come up with such administrative laws for emergencies long ago.
Yes, governors just can't make up anything they dream of on a capricious whim. But when there's an emergency, they have the power to make up laws regarding that emergency as given them previously by the legislature. Administrative decrees based on emergency power laws are given deference by judges unless it's a very clear overreach.
So... yeah. Not following your governor's emergency directives can be criminal and lead to fines/imprisonment.
You're welcome to test it the next time your local administrative official declares a curfew in response to an emergency and you just stay out as long as you like. You can explain to the judge that that wasn't a real law because the time of that curfew wasn't passed by your local council or legislature. See how that goes.