President Donald Trump expanded his attacks on major U.S. law firms on Tuesday as he signed an executive order targeting Jenner & Block, which represents clients challenging some of his major policies and formerly employed a prosecutor involved in a special counsel investigation of his 2016 campaign.

The chair of a law firm that struck a deal with President Trump said the president’s executive order could have easily “destroyed our firm.” Chair Brad Karp told employees in a memo obtained by The Hill that he made an agreement with Trump that included pro bono support for the administration’s plans.