Felipe Massa was penalised during the Brazilian Grand Prix because he contravened a track limits rule clarified in the build-up to the race.
Interlagos's unusual pit entry has been a contentious topic for many years, as the racing line on the left-hand kink leading onto the pit straight crosses it.
This has led to fears of an accident if a car flat-out on a flying lap came upon a car slowing for the pitlane speed limit.
Just over an hour before Sunday's grand prix, FIA Formula 1 race director Charlie Whiting issued a clarification of the rules regarding that section of track.
An image sent to teams marked an area of the white line from parallel with the end of the left-hand-side Armco barrier to the start of the pitwall as the 'track edge', and ordered that cars could not cross it with all four wheels.
It was this line that Massa was judged to have crossed illegally, prompting the drive-through penalty that dropped him from fourth to an eventual seventh in his Ferrari farewell.
The proceeding section of white line leading up to 'point c' in the FIA image was labelled part of the pit entry and was fine to cross on a fast lap.
Massa, in his final race for Ferrari before moving to Williams, admitted he had breached the rule, but argued that others had done the same and that the regulation had been created ad hoc.
"Sure, I crossed the line a few times, but maybe I was not the only car that crossed there. and this rule is something they've invented now," he said.
"If you really need to do that, then you should penalise everybody who passed it."
Asked by AUTOSPORT if Ferrari had received a proper warning before the penalty, team boss Stefano Domencali said: "Yes, there was a warning but it was very harsh.
"There was not really any safety aspect, there was not really any gain of any kind of advantage.
"You see many times track limits not respected. But anyway, that decision was taken and it was very harsh considering the result."