Kendall Jenner Pepsi Ad May Have Crossed Legal Line with San Francisco Police Dept.

Kendall Jenner's Pepsi ad has cops on the soda company's tail ... cops from the police department depicted in the video.

You see an emblem on the cop's shirt sleeve with the words, "San Francisco Police." There's also an eagle spreading its wings ... pretty much like the real SFPD uniforms except the color scheme is different.

Sources at the San Francisco PD tell us Pepsi never asked permission to mimic their uniforms. What's more, the sources say they're working with the City Attorney to determine if producers crossed the legal line by using the logo, which the City considers proprietary.

True enough ... pics of the emblem are featured in behind the scenes footage of the making of the commercial -- footage that was released online and got lots of views, and might now land producers in even more hot water.