All I can say is my bike came from the factory with the short ones so if they are not leagal its not on me! Really dont think any cop will be offended by the noise and want to pull me over as they really are not loud at all.
The problem over here Paul is that the test inspectors for the yearly MOT test won't pass a bike with 'not for road use' or similar marked on the cans and also the police have started pulling over bikes to check MOT conformity. Nice eh? So whereas it was possible to put your standard cans on just for the test, the police are trying to close that loop hole.