He is a founder of the Home School Legal Defense Association (HSLDA) and Patrick Henry College, which share a campus in Purcellville (Loudoun County), Virginia.

Farris has argued for the petitioners in the Supreme Court cases Witters v. Washington Department of Services For the Blind in 1985–1986[7] and National Institute of Family and Life Advocates v. Becerra in 2018.

Farris' close connection to conservative leaders like Jerry Falwell of the former Moral Majority, Pat Robertson of the Christian Coalition and Phyllis Schlafly of the Eagle Forum stirred deep-seated feelings about religion and politics.

[11] Apportionment.us brought the case in attempt to apply the "One Man, One Vote" principle of Baker v. Carr to the relative size of congressional districts across state lines.

He served as senior fellow for constitutional studies for the project's parent organization, Citizens for Self-Governance, and as a member of CSG's legal board of reference.

[15] On October 1, 2022, Kristen Waggoner succeeded Farris as CEO and President of ADF, retaining her role as General Counsel.