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 executive order naming Jenner & Block aims to probe its security clearances, government contracts and access to federal buildings. Last week, a federal judge blocked parts of a similar executive order against another prominent firm.