The American Constitution Society for Law and Policy (ACS) is a left-of-center legal activist group that aims to frame the United States Constitution as a document whose meaning shifts based on historical and political circumstances and that lawmakers should apply its articles and amendments accordingly. To advance this view, often called “living constitutionalism.” ACS hosts discussions and other public events, provides networking opportunities to its supporters in the legal and policymaking fields, and generates talking points for activist lawyers. The ACS touts its preference for recruiting individuals from ethnic and sexual minority backgrounds and recommends that its members implement hiring and mentoring practices that favor these minority groups.
ACS has been described as a “liberal Federalist Society” – a reference to the prominent right-leaning and “originalist” legal advocacy organization. ACS maintains ties with the Democracy Alliance, a network of left-of-center philanthropists and institutional donors that has injected nearly $2 billion into its favored causes since its founding in 2005. The ACS has also received funding from the Tides Nexus, another major left-of-center grantmaking collective, as well as the Open Society Foundations of financier and activist philanthropist George Soros. The organization’s willingness to accept funding from global mega-corporations such as Amazon, Facebook, Google, and Microsoft has earned it criticism from other left-of-center activists who oppose corporate influence on politics.
The American Constitution Society was founded in 2001 in order to promote a liberal, “living” interpretation of the United States Constitution. David Strauss at the University of Chicago describes a “living constitution” as “one that evolves, changes over time, and adapts to new circumstances, without being formally amended.” 
American Constitution Society had substantial influence during the Obama administration. President Obama’s first Attorney General, Eric Holder, was a board member of ACS. Former White House staff secretary Lisa Brown, Domestic Policy Council head Melody Barnes, and Vice President Joe Biden’s former chief of staff Ron Klain also had ties to the organization. ACS also had members on the Obama transition team, and the New York Times speculated that other ACS members would be used to fill judgeships.
After the election of President Donald Trump, the ACS rallied progressive activists in opposition to Trump’s judicial nominees. The group held a conference call with progressive activists and urged them to encourage Democratic U.S. Senators to stall President Trump’s nominees. This was a reversal from ACS’s position from the Obama administration, during which the ACS complained about the stalling of President Obama’s judicial nominees.
ACS has also joined with other organizations to form a left-wing state-policy think tank. In 2015, the ACS’s “American Legislative and Issue Campaign Exchange” joined with two other similar groups to form the State Innovation Exchange. All three groups received a combined total of $9.1 million from George Soros and organizations associated with the liberal billionaire, with ACS receiving $5.8 million. 
Following the 2020 general election, American Constitution Society began campaigning and lobbying for President Joe Biden to fill judicial vacancies with left-of-center judges. Its goal was to take advantage of the Democratic control of the Senate by appointing as many liberal judges as possible while also making up for lost opportunities to do so during President Barack Obama’s presidency.
As of 2022, Russ Feingold was the president of the American Constitution Society. He was a Wisconsin state Senator between 1983 to 1993, and a United States Senator for Wisconsin from 1993 to 2011. Feingold co-sponsored the Bipartisan Campaign Reform Act, commonly known as the McCain-Feingold Act, a major piece of election finance legislation. He was also the only Senator who voted against the initial version of the controversial 2001 Patriot Act, and was a vocal opponent of the Iraq War.
Feingold supports expanding the legality and availability of abortion and claimed that the 2022 Supreme Court decision overturning the controversial decades-long pro-abortion precedent set by the Roe v. Wade decision would lead to “devastation.” He also claimed that the Supreme Court, which has consisted of nine justices since the mid-19th century, was unfairly “packed” to achieve this outcome.
Prior to Feingold, Caroline Fredrickson led ACS. She is a former legal director at NARAL Pro-Choice America (formerly the National Abortion Rights Action League). She also served as chief of staff to U.S. Senator Maria Cantwell (D-Washington). She is a senior fellow at the left-of-center Brennan Center for Justice. 
The single largest backer of the American Constitution Society is George Soros’s Open Society Network. Other major funders include some of the most influential grantmakers on the political left, including the William and Flora Hewlett Foundation, the Bernard and Anne Spitzer Charitable Trust, and the Democracy Fund.
From 2015 through 2020, the ACS’s annual revenue fluctuated between $4.5 million and $8.2 million.