Following the passage of the Landrum-Griffin Act, Jenkins served as the Assistant Commissioner of the Bureau of Labor Management Reports where he was the highest-ranking African American lawyer working in the federal government.

George Johnson, the dean of Howard University Law School, asked Jenkins to join the faculty.

[5] Jenkins then went to work in Washington, D.C. for William Willard Wirtz on the National Wage Stabilization Board, and joined the faculty at Howard University School of Law.

As a law professor he helped prepare briefs for the U.S. Supreme Court to desegregate the railroads and the public schools, including the landmark case of Brown v. Board of Education.

While special assistant, he was intimately involved in drafting and passing the Landrum-Griffin Labor Reform Act, known as the Employees' Bill of Rights.

In 1963, Jenkins became the first African American to be appointed to the U.S. National Labor Relations Board (NLRB) when nominated by President John F. Kennedy.

He wrote the majority opinion in the 1964 watershed case Hughes Tool Co. II, which created unions' duty of fair representation.