The American Constitution Society for Law and Policy (ACS) is a legal organization that is often considered the liberal version of the center-right Federalist Society. The group endorses the left-of-center view of the Constitution as a “living document,” capable of substantial judicial interpretation that critics see as improper legislating from the bench.
The ACS 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.” 
The ACS had substantial influence during the Obama administration. Former Attorney General Eric Holder was a board member of the ACS. Former White House staff secretary Lisa Brown, Domestic Policy Council head Melody Barnes, and Vice President Joe Biden’s former chief of staff Ronald Klain also had ties to the organization.  The 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 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.
The ACS has also joined with other progressive organizations to form a progressive 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 the ACS receiving $5.8 million. 
In 2015, the ACS raised $2.6 million and spent $4.6 million. The largest single expenditure was $1.6 million for “network advancement.” This was money used to support the operations of ACS chapters on the state and local level. The goal was to build a more progressive legal community. The ACS spent $738,484 on public education and outreach and $718,044 on policy development and programming
The ACS made a $75,000 contribution to the Committee for a Fair Judiciary. It made $10,000 grants to the Mercer School of Law at Indiana University and the Prison Policy Institute.
The ACS President is Caroline Frederickson. 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).