Upon graduation from the Naval Academy, Schmitz served in the U.S. Navy for approximately four years, including a stint as an exchange officer with the German Navy. After leaving active duty, Schmitz went to law school, and was in the Naval Reserve until 2001. He clerked with James L. Buckley, Circuit Judge for the D.C. Circuit Court, and was a special assistant to Attorney General Edwin Meese III during the Reagan Administration. Schmitz entered the private sector in 1987, eventually joining the Patton Boggs law firm in Washington, D.C. He was also an adjunct professor of law at Georgetown University in the 1990s, and founded his own firm, Joseph E. Schmitz, PLLC, in 2008.