As the student leader at the Pontifical Catholic University of Chile, he participated in the 1927 riots against Carlos Ibáñez del Campo's dictatorship, which was deposed in 1931. During the same year, Leighton was sent by the Minister Marcial Mora to Coquimbo to placate the local military riots supported by the population. In 1933, he graduated as a lawyer with a thesis on rural works.