Apple have recently added a new question into the iTunes Connect flow when submitting a new app, or an update to an existing app.
"Does your app contain, display or access third-party content?"
If you answer "No", you can continue with the submission, if you answer "Yes" you are asked a further question, "Do you have all necessary rights to that content or are you otherwise permitted to use it under the laws of each App Store territory in which your app is available (for example, fair use).
If you answer "Yes", you can continue, if you answer "No" you are shown a warning, and a link to the trademarks section of the App Store Guidelines.
This doesn't appear to be any new policy on Apple's part, but we can guess that Apple is planning to enforce the guidelines more strictly in future, in particular guideline 8.5:
This seems most likely to affect apps which use the brand names or logos of other companies, for example apps which show fashion products, sports teams, TV network logos, etc. Be prepared to submit written documentation that you have the right to show such content, even in the past Apple has not rigorously required this.