In 2021, Brennen graduated from the Mississippi College School of Law with a Juris Doctor. While in law school, Brennen served as vice chair of the moot court team, both competing and coaching on the local and national levels. During his final year, Brennen was admitted to practice to the Jackson, Mississippi criminal court where he defended felony trials.
Following his 2021 law school graduation, Brennen earned in 2022 a Master of Law in Taxation from University of Houston School of Law. While attending, Brennen worked with the Senior Judge of the United States Tax Court, the Honorable Juan F. Vazquez, Sr.