Thrust is derated by the use of program plugs on the EEC's
It depends on the engine, but the program plugs deliver the RATED THRUST.
the pilot does not have access to rated thrust.
Once again the answer is that it depends on the engine, you will find that a lot of aircraft operate with Fixed Derate and Assumed/Flex Derate which are lower than the RATED THRUST and are controlled by the pilot.
Mutt