YouTubers in the UK are being told they need to be more clear when they are paid to promote products.
The Advertising Standards Authority ruled that videos by Emma Blackery, Phil Lester, PJ Liguori and Tom Ridgewell broke the rules.
The YouTubers all made videos promoting Oreos back in June.
The ASA said the videos were not clearly labelled as adverts, which is against the law.
It’s the first time the ASA has made a ruling like this on a YouTube campaign.
Lynsay Taffe from the ASA told BBC News: “Brands and vloggers now have to make it very clear, before you click on a video, that it’s a promotional video.”
That means YouTubers should write “this is a paid for advertisement” in the video description, or use the word “advert” in the video title.
The ASA said it had to be completely clear, so a disclaimer couldn’t be buried at the bottom of the description box or appear at the end of a video.
The company that makes Oreos told the BBC it would “ensure the adverts did not appear in their current form again”.
YouTube said creators are responsible for making videos that stick to local laws and regulations.
The Oreo videos have now had their descriptions changed to include the text “this is a paid for advert”.