After finishing his pre-law at the University of Santo Tomas, Reyes took up his law degree at the San Beda College of Law where he, together with now fellow Supreme Court Justice Jose C. Mendoza, established the law fraternity Lex Talionis Fraternitas.
In July 1990, he became Presiding Judge of the Regional Trial Court of Malabon and was appointed Associate Justice in the Court of Appeals on August 8, 2000.