I would highly not recommend casting a hook less fly on closed waters, most wardens would frown upon this. If you were to cast a fly in this situation I'd make sure it was a undesirable presentation to the river bound fish at the time. I attend some of the clinics and end of the months meet and greets on the Sky when I have nothing else going on and 95% of the people who attend use yarn and for the guys just learning with Skagit heads we'll double the yarn up for them