In a memorandum to US Attorney General Pam Bondi on Friday, Trump said lawyers were helping to fuel "rampant fraud and meritless claims" in the immigration system, and directed the Justice Department to seek sanctions against attorneys for professional misconduct.
The order on Saturday also took aim at law firms that sue the administration in what Trump, a Republican, called "baseless partisan" lawsuits.
He asked Bondi to refer such firms to the White House to be stripped of security clearances, and for federal contracts they worked on to be terminated.
Ben Wizner, a senior lawyer at the American Civil Liberties Union (ACLU), said the new directive sought to "chill and intimidate" lawyers who challenge the president's agenda.Â
Trump has separately mounted attacks on law firms over their internal diversity policies and their ties to his political adversaries.
"Courts have been the only institution so far that have stood up to Trump's onslaught," Wizner said.
"Courts can't play that role without lawyers bringing cases in front of them."
The ACLU is involved in litigation against the administration over immigrant deportations, including the expulsion of alleged Venezuelan gang members.
The Trump administration has been hit with more than 100 lawsuits challenging White House actions on immigration, transgender rights and other issues.
Legal advocacy groups, along with at least 12 major law firms, have brought many of the cases.
A White House spokesperson, Taylor Rogers, said "President Trump is delivering on his promise to ensure the judicial system is no longer weaponised against the American people".
The Justice Department directed Bondi to assess lawyers and firms that brought cases against the government over the past eight years.
Law firm Keker, Van Nest & Peters, which is working with the ACLU in an immigrant rights case against the administration, said in a statement that it was "inexcusable and despicable" for Trump to attack lawyers based on their clients or legal work opposing the federal government.
Trump issued executive orders this month against law firms Perkins Coie and Paul Weiss, suspending their lawyers' security clearances and restricting their access to government buildings, officials and federal contracting work.
The president also suspended security clearances of lawyers at Covington & Burling, in each case citing the firms' past work for his political or legal opponents.
The Keker firm on Saturday called on law firms to sign a joint court brief supporting a lawsuit by Perkins Coie challenging the executive order against it.
Lawyers for Civil Rights, a legal advocacy group suing the administration over deportations, called Trump's sanctions threat hypocritical in a statement to Reuters, saying Trump and his allies "have repeatedly thumbed their noses at the rule of law".
