President Donald Trump’s retweet of a series of anti-Muslim videos posted by a leader of a far-right group in the U.K. risks undermining his travel-ban defense a week before two federal appeals courts are set to to hear challenges to the directive.

Iranian Alliances Across Borders, one of the nonprofit groups suing Trump over the travel ban, will “almost certainly” use the president’s retweet to support its case, attorney Sirine Shebaya said. Other plaintiffs will “absolutely” use them as evidence that the third version of the ban, which makes no reference to religion, is actually motivated by animus toward Muslims, said Peter Spiro, an immigration law professor at Temple University in Philadelphia.

“President Trump is just about the worst client one could have as a lawyer,” Spiro said. “He just doesn’t get it, in terms of how these kinds of public statements can come back to bite the administration in court.”

The federal appeals court in San Francisco is set to hear a challenge to the ban on Dec. 6, and the appeals court in Richmond, Virginia, will hear another case two days later. Both suits, filed by states and plaintiffs groups representing Muslims and immigrants, say the ban is unconstitutional because it targets a particular religion and violates federal immigration law.

“The tweets reinforce and illustrate our point that the president’s actions are motivated by anti-Muslim animus,” Shebaya, with Muslim Advocates, said in an email. “They are therefore highly relevant to the Muslim-ban cases.”

EVIDENCE WEIGHING

Joshua Wisch, a spokesman for Hawaii Attorney General Doug Chin, whose lawsuit over the ban will be heard in San Francisco, declined to say if Trump’s retweet will be featured in the case. However, Chin responded to Trump with a tweet of his own.

“President Trump’s decision to retweet white nationalist anti-Muslim tweets just goes to show he meant it when he said he wanted to ban all Muslims from the country,” Chin tweeted. “It’s against our founders’ ideals and it’s un-American.”

Trump’s negative comments about Muslims on the campaign trail, including a promise to halt Muslim immigration into the U.S., have been used extensively to win injunctions against the earlier bans.

A representative from the Justice Department didn’t immediately return a call.

The videos retweeted by Trump were posted by Jayda Fransen, the deputy leader of Britain First, a nationalist group that campaigns against what it calls the Islamification of the U.K. One purports to show a “Muslim migrant” assaulting a Dutch person on crutches, while another shows an “Islamist mob” pushing a teenage boy off a roof. A third purports to show a Muslim man destroying a statue of the Virgin Mary.

White House deputy press secretary Raj Shah said Trump addressed the issue of whether Muslims are a threat to the U.S. by issuing the travel-ban order.

“It’s never the wrong time to talk about security and public safety for the American people,” Shah told reporters on Air Force One.

Hans von Spakovsky, a lawyer at the conservative Heritage Foundation, said Trump’s retweets won’t undermine the government’s careful analysis of which countries are failing to provide the U.S. with sufficient information to vet incoming aliens.

“The order goes into great detail of the thorough and extensive process the Department of Homeland Security engaged in to review the credibility and trustworthiness of the information we receive,” von Spakovsky said. “Tweets showing the heinous acts of some individuals is not going to change that.”

LEGAL ANALYSIS

When Trump issued the third version of the travel ban, many legal experts said it had a solid national-security foundation that effectively insulated the directive from flaws found in the two earlier versions, which were struck down by appeals courts. One appeals court ruled it was “steeped in animus,” while another held it ran afoul of a federal law prohibiting nationality-based discrimination.

The ban limits travel from Iran, Libya, Somalia, Syria, Yemen, Chad, Venezuela and North Korea. The third iteration of the travel directive would almost surely pass muster if it had been offered by any other president, according to Spiro.

“The argument is that these actions are motivated by religious animus, and Trump’s statements and tweets supply the evidence for that, even though on their face the second and third travel bans are neutral as to religion,” Spiro said.

Mark Krikorian, executive director of the Center for Immigration Studies, a Washington-based think-tank that supports Trump’s immigration policies, said federal law grants the president broad authority to keep out aliens “for any reason he wants,” including anti-Islam views.

“There are all kinds of costs that a president could pay for what his critics are alleging, but there are no legal costs,” Krikorian said. The president’s retweet “has no bearing on his authority to issue these travel bans.”