The American Civil Liberties Union (ACLU) vowed to sue Jeff Sessions Jefferson (Jeff) Beauregard SessionsTrump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status White House officials voted by show of hands on 2018 family separations: report MORE if he violates the Constitution immediately after he was confirmed by the Senate as attorney general.

“If he violates the Constitution, we’ll sue,” the ACLU tweeted on Wednesday night.

BREAKING: Jeff Sessions confirmed as attorney general.



If he violates the Constitution, we'll sue. pic.twitter.com/le02tuG2Pg — ACLU National (@ACLU) February 9, 2017

The ACLU launched the first successful lawsuit against the Trump administration in late January when it filed a complaint on behalf of two men who were detained at an airport as a result of Trump’s controversial executive order barring travel from seven predominantly Muslim countries to the U.S.

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A federal judge filed an emergency stay on parts of the executive order at the time as a result.

The group has received a flood of donations and is setting itself up as one of the key players in coming legal fights over Trump's agenda.

Sessions was confirmed by the Senate after a contentious all-night debate about his nomination. Sessions, a Republican senator from Alabama, was eventually confirmed in a 52-47 vote.

The vote came after Sen. Elizabeth Warren Elizabeth WarrenNo new taxes for the ultra rich — fix bad tax policy instead Democrats back away from quick reversal of Trump tax cuts It's time for newspapers to stop endorsing presidential candidates MORE (D-Mass.) was barred from speaking on the Senate floor against Sessions Tuesday night. Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellSenate Republicans signal openness to working with Biden Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll The Hill's Campaign Report: Biden asks if public can trust vaccine from Trump ahead of Election Day | Oklahoma health officials raised red flags before Trump rally MORE (R-Ky.) said her speech, in which she was reading a letter by the late civil rights activist Coretta Scott King against Sessions's federal judgeship nomination in the 1980s, was impugning another member of the Senate.