The Landmark Legal Foundation is a right-leaning public interest law firm and advocacy organization that has offices in Kansas City, Missouri, and Leesburg, Virginia. The organization was founded in 1976 and has filed cases in various courts challenging Environmental Protection Agency regulations, combating teachers unions such as the National Education Association, and limiting the powers of the federal judiciary. 
Conservative talk radio and Fox News television show host Mark Levin was the organization’s president from 1996 until 2017 and remains a board member of the organization. 
The Landmark Legal Foundation was founded in 1976 with a focus on protecting individual liberty and promoting conservative principles. The organization also has several advocacy programs that promote center-right policy positions and provide opposition research critical of left leaning unions and the Environmental Protection Agency. The group’s Judicial Reform Initiative advocates to reign in alleged overreach of federal courts that the foundation maintains have been a result of activist left-leaning judges abusing the commerce clause and other parts of the U.S. Constitution to create laws from the courts. Additionally, the foundation has an Environmental Accountability Project that has advocated for increased access to government records and created a database of grants to left-leaning environmental organizations from federal agencies. 
The Landmark Legal Foundation has also long been critical of the National Education Association (NEA), left-leaning teachers union. In 2002, the Foundation filed a complaint with the Internal Revenue Service and the Department of Justice recommending a criminal investigation against the union for not complying with political activity and funding disclosure laws.  The filing ultimately resulted in the NEA opening more records to the public. 
Much of the Landmark Legal Foundation’s current work centers on filing amicus briefs in Supreme Court and U.S. Court of Appeals cases. The organization filed an Amicus Brief in a case before the U.S. Court of Appeals for the Ninth Circuit supporting construction of the Trump administration’s proposed border wall on behalf of families of individuals murdered by illegal immigrants. The organization also filed an amicus brief in Janus vs. AFSCME supporting the ability for employees to opt out of paying dues to public sector unions. 
In 2012, then President of the foundation Mark Levin worked on behalf of the foundation to call for an investigation into the IRS’s alleged targeting of conservative groups making the organization among the first to call for an investigation. The investigation later revealed that the IRS singled out groups with terms including “tea party” and “patriot” in their names. 
Following the 2020 election, the Landmark Legal Foundation filed a brief supportive of challenges to the results of the Presidential election results in Pennsylvania under claims that the state’s mail-in voting program violated the state constitution. 
Conservative talk show host Mark Levin worked as president of the Landmark Legal Foundation from 1996 to 2017, when he stepped down to focus on hosting his Fox News show “Life, Liberty and Levin.” Levin remains on the board of the foundation. During the Reagan administration, Levin served as chief of staff to Attorney General Edwin Meese, who also sits on the foundation’s board. The foundation’s board of advisors also includes Becky Norton Dunlop of the Heritage Foundation and Larry Arnn, the president of Hillsdale College. The late conservative economist Walter Williams also served as an advisor to the organization.