Facebook has refused to run an ad critical of founder Mark Zuckerberg's apparent support of the Keystone XL pipeline.

Zuckerberg is one of the co-founders of FWD.us, an organization pushing for immigration reform, which — according to the Center for American Progress — has been funding ads in support of TransCanada's contentious Keystone XL pipeline.

But when activist group CREDO Action tried to buy space on Facebook for an ad asking Zuckerberg to stop running the pro-Keystone commercials, Facebook said no.

The official reasoning for declining the ad was that it uses Facebook trademarks — i.e. Zuckerberg's face.

Facebook declines “ads that contain Mark’s image because — not surprisingly — in our experience those ads tend to be confusing for users, and frequently misleading," according to a statement from the company run by The Washington Post.

"Users may click on the ad thinking it is a message from Mark or from Facebook, not understanding that they are actually in an advertisement seeking to take advantage of Mark’s image."

But the ad's purpose was to call out Zuckerberg's funding of pro-Keystone XL Pipeline ads. FWD.us pays for two subsidiary groups, one Republican and the other Democrat, who are pushing the group's objectives.

The Republican group, Americans For A Conservative Direction, made an ad in support of South Carolina Republican Senator Lindsey Graham, celebrating his support of the pipeline's construction. Their website contains little more than immigration reform information and the FWD-funded ad.

CREDO has criticized Facebook and Zuckerberg's political involvement in the past. The group protested outside Zuckerberg's home in February after he held a fundraiser for New Jersey Governor Chris Christie. Later, CREDO set up a Facebook ad campaign to oppose "how political Mark Zuckerberg has become,” according to Politico.

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