During law school, Lester worked for Senator Bob Dole and served on President Ronald Reagan’s Transition Team for the Equal Employment Opportunity Commission. In 2002-2003, Lester chaired Oklahoma Governor Brad Henry’s Law Enforcement/Corrections Transition Team and was a member of the Budget/Finance Transition Team, where he helped write Governor Henry’s first State budget. In 2008, Lester was retained as Special Counsel by the Oklahoma House of Representatives to represent a bipartisan Special Investigating Committee concerning the impeachment of the State Auditor and Inspector. In 2011, the Oklahoma House of Representatives turned to him again to represent a bipartisan Special Investigative Committee to review ethics allegations against a House Member. He has also served as Acting General Counsel of the Oklahoma House of Representatives.

Representative published opinions include Wilson v. Fallin, 2011 OK 76, 262 P.3d 741 (upholding Oklahoma Senate redistricting law, Alexander v. Taylor, 2002 OK 59, 51 P.3d 1204 (adopting Republican Congressional redistricting plan); Gann v. Cline, 519 F.3d 1090 (10th Cir. 2008) (establishing First Amendment protection for political non-affiliation); FTC v. Kuykendall, 371 F.3d 745 (10th Cir. 2004) (en banc) (reversing with instructions $39 million contempt citation); Plain v. Murphy Family Farms, 296 F.3d 975 (10th Cir. 2002) (affirming $2 million wrongful death verdict); Pabst v. O. G. & E., 228 F.3d 1128 (10th Cir. 2000) (affirming $1.3 million Fair Labor Standards Act judgment); Moore v. City of Wynnewood, 57 F.3d 924 (10th Cir. 1995) (accepting pendent appellate jurisdiction and reversing denial of qualified immunity); Juvenal v. Okeene Public Schools, 1994 OK 83, 878 P.2d 1026 (establishing premises liability standard under Governmental Tort Claims Act); Housing Authority of the Kaw Tribe of Indians v. City of Ponca City, 952 F.2d 1183 (10th Cir. 1991) (holding a political subdivision has no constitutional claim against another political subdivision). Lester has been licensed to practice before the highest courts of Oklahoma, Colorado, Texas and District of Columbia.

From 1988 to 1996, he served as a United States Magistrate Judge for the Western District of Oklahoma. An Adjunct Professor at Oklahoma City University School of Law since 1988, Lester has taught State & Local Government Law, Employment Law, Criminal Law and International Law. He is an Adjunct Scholar of the Oklahoma Council of Public Affairs.

Lester has written more than 100 articles on professional and public policy issues. The Organization for Security and Cooperation in Europe and the American Bar Association’s Central & East European Law Initiative published his book, Constitutional Law and Democracy, a collection of speeches he gave in the former Soviet Union, in English, Russian and Romanian.

He chairs the Board of Regents for the Oklahoma Agricultural and Mechanical Colleges, which oversees Oklahoma State University, Langston University, Oklahoma Panhandle State University, Connors State College and Northeastern Oklahoma A&M College. Appointed to the Board of Regents in 2007, he was reappointed to a full eight-year term in 2010, winning unanimous confirmation in the Oklahoma Senate. 

Lester also serves as Chairman of the Board of Trustees of Langston University-Oklahoma City and Langston University-Tulsa. He also chaired the Langston University Presidential Search Committee in 2011-2012. He was previously a member of the Board of Trustees of Eureka College, President Reagans's alma mater. 

Lester chairs the Oklahoma Advisory Committee of the United States Commission on Civil Rights. He is a former Chairman of the Board and President of the Historical Society of the Tenth Judicial Circuit, and continues to serve on its Board of Directors.  He twice served as President of the Oklahoma Association of Municipal Attorneys, and was a long-time member of its Board of Directors. He has served on the boards of the Federalist Society’s Civil Rights Practice Group, the Salvation Army - Oklahoma City Command, and St. Mary’s Episcopal School of Edmond. Formerly a resident of Enid, he chaired its Police Civil Service Commission, and was a member of the boards of the Booker T. Washington Community Center, Enid Habitat for Humanity, and the Martin Luther King, Jr., Holiday Commission.

In 2012, Lester was named Edmond's Citizen of the Year. He is a past President of the Rotary Club of Edmond, and, in 2011, received the George Mikesell Award as Rotarian of the Year. He has been listed in Who’s Who in the World, Who’s Who in America, Who’s Who in American Law, and Who’s Who in the South and Southwest.

Lester has appeared as counsel before committees of the United States Senate and the United States House of Representatives, and faced off against the White House over a highly publicized controversy on the use of Executive Privilege. He has been interviewed by virtually all major media outlets, including ABC, CBS, CNN, NBC, The New York Times, The Washington Post, and the Associated Press. He has been a featured guest on television shows such as MSNBC’s Hardball with Chris Matthews and CNN’s The Situation Room with Wolf Blitzer.