▶ Watch Video: Tech experts say proposed Trump social network faces many challenges Washington — Stephen Miller, who was a top aide to former President Donald Trump and the driving force behind his hardline immigration policies, has launched a new legal group that aims to take the fight against President Biden and Democrats’ agenda to the courts. The group, America First Legal Foundation, was unveiled Wednesday with the backing of Mr. Trump and a board of directors that includes former White House chief of staff Mark Meadows and former acting Attorney General Matt Whitaker, as well as others with deep ties to the conservative movement. “Those who believe in America First must not shy away from using our legal system to defend our society and our families from any unlawful actions by the left,” Miller said in a statement. “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.” Miller’s new group aims to use the legal system to challenge Mr. Biden’s policies and fight back against attempts to dismantle the former president’s initiatives and the conservative agenda. The organization plans to use attorneys who worked in the Trump administration and partner with state attorneys general to help mount legal battles against Democrats’ agenda. “As we know, the Radical Left has been relentless in waging their battles in court. Conservatives and America First supporters badly need to catch up and turn the tables, which is why I applaud Stephen and Mark Meadows for rushing to fill this critical void,” Mr. Trump said in a statement supporting Miller’s new venture. Mr. Biden has been in office less than 100 days, and Republican attorneys general have wasted no time in filing legal challenges to the president’s executive actions, vowing to use the courts to stymie his agenda. With Mr. Trump appointing more than 230 judges to the federal bench and three justices to the Supreme Court, Mr. Biden’s initiatives are on a possible collision course with the federal judiciary remade by his predecessor. Mr. Trump, too, saw considerable pushback to his policies in the federal courts across his four years in office. The American Civil Liberties Union filed more than 400 legal actions against the Trump administration, and many of his efforts were blocked by the lower courts. The Supreme Court took up numerous disputes over Mr. Trump’s policies, including his order to end the Deferred Action for Childhood Arrivals (DACA) program, his so-called travel ban and attempt to add a citizenship question to the 2020 census. The former president had a mixed record before the nation’s highest court — the justices upheld the travel ban, but blocked his rescission of DACA and addition of the citizenship question to the decennial census. Miller’s new organization is the latest initiative from former members of the Trump administration. Earlier Wednesday, former Vice President Mike Pence unveiled a new group that seeks to counter Mr. Biden’s and the Democratic-controlled Congress’ policies.