That is the claim of Germany's Auto Motor und Sport, on the day the German driver was reportedly instructed to change his celebratory helmet because it included an image of the famous world cup trophy.
World football federation FIFA contacted the Rosberg camp to inform him his proposed helmet was an "unauthorized reproduction of its intellectual property".
Rosberg told his Twitter followers the news is a "shame, but of course I respect the legal situation".
He has replaced the trophy image with a simple star, and told reporters at Hockenheim that the fuss left him surprised.
"The world cup as a trademark — these are the kind of things you have to think of. It's amazing," said the Mercedes driver.
"I've replaced it now with a big star and no one can take that away. The star is ours!"
A FIFA spokesman confirmed Thursday's news, but Auto Motor und Sport reports that there was another complainant behind the story — Hyundai.
Rosberg drives for Mercedes, but affiliation between the world cup and a car manufacturer is promised exclusively to Hyundai, the official sponsor.
Indeed, Mercedes made clear its delight with Germany's world cup win on Thursday with a huge message on its F1 motor home, reading "Das Beste" and congratulating the national football team on its "Title win".
But no mention was made of the world cup itself, or its protected marks.
07/17/14 (GMM) Nico Rosberg has modified his proposed world cup-themed helmet ahead of the German grand prix.
Earlier, the championship leader announced he would celebrate Germany's win by wearing a special helmet at Hockenheim this weekend featuring an image of the famous world cup trophy.
But we reported earlier that reproducing the image of the trophy falls foul of the world football federation FIFA's strict rules protecting its 'official marks'.
The Mercedes driver's public relations manager Georg Nolte confirmed: "There will be an update on Nico's Germany helmet design today.
"(It) will be without (the) world cup trophy, but (now) with four stars on it."
The four stars correspond to each of Germany's world cup wins, in 1954, 1974, 1990 and now 2014.