The FIA has fined Prema Powerteam after the team's Mercedes junior Maximilian Gunther carried out DTM 'taxi' rides at the recent opening round at Hockenheim.
New rules for the Formula 3 European Championship ban any driver from driving cars on any upcoming circuit on the F3 calendar, unless the governing body has been notified at least 30 days beforehand.
Prema did not give sufficient notice that Gunther would be carrying out the activities at Hockenheim, which hosts the final round of the F3 championship in October.
Prema was fined €2500, with €2000 suspended until the end of the season.
The officials' statement said: "Having considered the matter extensively, the stewards have decided that the driver was participating in a genuine promotional event driving VIP guests in a car.
"It was a genuine misunderstanding by the driver in respect that article 22.6 applied to <all> motorised vehicles at any track on the FIA F3 calendar."
The punishment is similar to that handed out to Carlin at Monza in the wake of Jake Dennis's previous outing at the Italian circuit in the Blancpain Endurance Cup.
Motorsport.com understands that BMW junior and Euro F3 championship leader Joel Eriksson ducked out of similar activities at Hockenheim for the Munich manufacturer because of the 30-day notice period.
The fine raised questions as to whether DTM manufacturers' F3 proteges will be allowed to participate in any DTM 'taxi' activities, especially on the weekends where the two series race together.
While the FIA did not want to comment officially on the matter, the indications are that this will be allowed as long as the notice period is respected, and the regulations state that the rule is not intended to stop drivers from competing in other championships or carrying out promotional work.
While Eriksson is likely to perform BMW duties at meetings where the DTM and F3 race together, Gunther said he would not.
"We made a decision together with Mercedes," he told Motorsport.com. "Where there is an F3 race weekend I will focus on F3. There was a bit of a confusion and misunderstanding about Hockenheim but now it is clarified.
"I really enjoyed driving the 'taxi', and I will again at Moscow Raceway [where F3 does not race], but not as much as I enjoyed the two-day young-driver test I did with Mercedes in the winter!
"It's just great to be a part of the Mercedes team, but I want to focus on F3."