Intl Mechanic Code 309.1 "Space-heating systems" clarification
Just because it isn't tweaked right doesn't mean the system is not "capable of maintaining..." 

afaik, it's applied when someone complains. Which they have the right to if the system cannot maintain a temp above 68, measured 3' off the floor. 

If it runs 24/7 and drops below 68 "on the design heating day" (w/e that means) then it does not meet code. If it has to be set at 90 to get 68, and it runs less than 24/7, never dropping below 68, then it meets code.

-"maintain", literally. If 90 is as high as the thermostat will go, and that can't keep it above 68, then it can't maintain. The system is either undersized, needs to be balanced, or can't deal with the heat loss.