****su you're right...I only used night because that was the example du jour.
The requirements for an IFR aircraft to accept and fly a visual approach are some of the most black and white in aviation...in fact they make a nice change...there is just no excuse for ad-libbing.
If the pilot thinks he can save 30 seconds by not complying with the star it is equally easy...ask for a vector direct 5 mile finals.
Either way a clearance to make visual approach while flying a star does not mean 'manouver as required' it simply removes the need for ATC to continue 'progressively clearing' the aircraft. The PIC can then track via the star and descend as required (wihin the night/day constraints) until he is on finals where he will be turned over to tower for a landing clearance.
Simple?
My recomendation stands...file reports...sitting behind your console muttering vague epithets about the pilots parentage achieve nothing. If you like they can be 'depersonalised'...just a a/c type and date. It won't be long before you see an improvement once the company C&Ting staff are made aware.