Stephen Miller, the one-time senior advisor to former President Donald Trump who shaped immigration crackdown policies, has launched a new conservative group that could take on President Biden's progressive agenda in court. 

Miller formed America First Legal, which aims to serve as a conservative counterweight to the American Civil Liberties Union (ACLU). The nonprofit organization intends to launch court challenges with state GOP attorneys general to fight back on executive actions they deem unlawful or an overreach. 

Miller understands firsthand the legal challenges that Trump faced when he sought to implement new executive policies, from his travel ban on predominantly Muslim countries to building a southern border wall with military funds.

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Miller called the anti-Trump court roadblocks a "years-long, one-sided legal assault" and argued conservatives now "must turn the tables."

"While radical progressives have wielded these tactics to undermine the law and America First values for years, we must deploy these tactics in defense of our nation’s legal, cultural, and constitutional heritage," Miller said in a statement

He added: "Those looking to hold the new administration in Washington to account finally have their answer. Our self-imposed policy of legal disarmament is now over."

FILE: WEST PALM BEACH, FL: White House Senior Advisor Stephen Miller arrives before the start of a news conference by President Donald Trump and Japanese Prime Minister Shinzo Abe hold a news conference at Mar-a-Lago resort on April 18, 2018 in West Palm Beach, Florida. The two leaders are meeting for a multi-day working meeting where they are discussing world events. (Photo by Joe Raedle/Getty Images)

FILE: WEST PALM BEACH, FL: White House Senior Advisor Stephen Miller arrives before the start of a news conference by President Donald Trump and Japanese Prime Minister Shinzo Abe hold a news conference at Mar-a-Lago resort on April 18, 2018 in West Palm Beach, Florida. The two leaders are meeting for a multi-day working meeting where they are discussing world events. (Photo by Joe Raedle/Getty Images)

In addition to Miller, former White House chief of staff Mark Meadows has joined America First Legal as a member of the board. 

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In a statement, Trump praised Miller as a "fearless, principled fighter for the America First movement."

He backed the new endeavor, saying Miller and Meadows are filling a "critical void" to take on the "Radical Left."

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"The era of unilateral legal surrender must end -- and I hope all America First patriots will get behind America First Legal," Trump said.

The new group intends to focus on executive branch actions and has recruited attorneys with such experience, including Gene Hamilton, who served in the Trump-era Justice Department.