I don't think they can. At least not any more than they can enforce flying manned aircraft without a Pilots Certificate. Here maanned aircraft don't even have to have ADSB-OUT.How will, or how could this be enforced, its not like a speed limit where at one time was enforced some what by radar traps ? I mean I can see it on new ones, but older ones not so much. Do you really think they have a way to control the non-compilers, there simply no way to control this ? What happens if joe farmer is still using his 5 yr old drone to check his crops on his land only, or the person who builds their own ?