[3] Lipez formerly served as a staff attorney in the United States Department of Justice Honor Program, Civil Rights Division, from 1967 to 1968.

[2] Lipez's judicial career began with his service as a justice of the Maine Superior Court, on which he served from 1985 to 1994.

He was appointed to the Maine Supreme Judicial Court in 1994, where he served until his investiture as a federal judge.

President Bill Clinton nominated Lipez to the United States Court of Appeals for the First Circuit on October 20, 1997, to fill a seat vacated when Judge Conrad K. Cyr assumed senior status.

He assumed senior status on December 31, 2011, and was succeeded by Judge William J. Kayatta Jr.[2] In August 2017, Lipez dissented when the en banc circuit, in an opinion by Judge Kayatta, rejected a lawsuit seeking to give Puerto Ricans the right to vote.