For those of mode S transponders - in UK, speed outside regulated airspace is now being watched..
How do they work out the IAS? The speed limit is IAS, not GS and not even TAS.
Not impossible but you would need to feed the winds aloft in real time into the software. Where would the wind data come from, accurate enough to prosecute? From airliner air data computers, but they fly thousands of feet (at least) above GA traffic. GA traffic with Mode S will not in 99% of cases be radiating any Enhanced parameters.
So I think this is a windup. The only traffic that could possibly be monitored would be CAT flying in Class G.