Formula One's governing body is to ban Ferrari's positioning of wing mirrors on the side of the 'halo' head protection device after allowing the Italian team to race with the novelty in Sunday's Spanish grand prix.
FIA race director Charlie Whiting told reporters a technical directive to that effect would be issued to teams, probably on Monday.
"I think it's a liberal interpretation of the word 'mounting'," he said of what Ferrari had done.
"That's how they've become legal because there's no bodywork allowed in the area ... the interpretation hinges on whether we think that's a mounting or not. We somehow think not, so we're going to take some action on that."
Asked whether such a solution, used for the first time in Spain and offering a likely measurable aerodynamic benefit, had effectively been banned, Whiting replied: "Yes, you could say that."
"If it was a clear breach of the regulations, they wouldn't have been allowed to use it here," he added. "But we'll clarify that to everybody."
Ferrari's Sebastian Vettel felt his team had done nothing wrong and the mirrors gave him a clearer view.
"For us it's straightforward. I see better. That was the point of moving them," the German told reporters after finishing fourth.
"We asked already in the beginning of the year when the first seat fit was with the halo if we can move them (the mirrors) on the halo because then they would just be in a better position to see what's behind."
Other teams saw the positioning of the mirrors as a way to circumvent strict rules on what can be attached to the bulky device that made its debut this season as a ring around the cockpit to protect drivers from flying objects.
"From a technical perspective, if it generates downforce it's a good thing," said Force India technical director Andy Green, speaking before the FIA made clear that Ferrari would have to move the mirrors.
"Should we be bolting aerodynamic devices to something that's supposed to be a safety device? I don't know. We were under the impression that was not legal."
