Immigrant rights lawyers are preparing to fight back against Donald Trump’s plans to carry out the largest mass deportation in U.S. history once he takes office again in January. The president-elect has already named some leading anti-immigration figures for his incoming administration who will lead the plan, including former ICE head Tom Homan and his longtime aide Stephen Miller. Trump’s picks were central in family separations, the Muslim ban, attacks on Deferred Action for Childhood Arrivals, or DACA, and other anti-immigrant policies during the first Trump administration. Trump is also reportedly planning to greatly expand immigrant detention in private for-profit prisons, and during the campaign he spoke of invoking the Alien Enemies Act of 1798 to speed up deportations. “We have been preparing nearly a year for this,” says attorney Lee Gelernt, deputy director of the ACLU Immigrants’ Rights Project, who argued some of the most high-profile immigration cases during the first Trump administration. He stresses that while groups like the ACLU will challenge the Trump administration in the courts, “it needs to be a national effort” to prevent abuses. “We are not opposed to basic immigration reform, but this cannot be a situation where we’re just going after immigrants left and right.”