Galarreta holds a Bachelor in Law and political science. From 1997 on he was committed to the NPO "Pro Education" of conservative National Renewal (RN) party leader Rafael Rey. He also joined Rey's party, the RN. In 1999 he represented the National Council for the Integration of Persons with Disability adjunct to the Labour Ministry. In 2002 he was elected councillor of Lima for a four-year term representing the National Unity (UN) alliance.
In 2006 he was elected to Congress for the 2006-2011 term for the same group. When the UN broke in 2008, Galarreta decided to stay on the National Unity bench, now congruent with the Christian People's Party (PPC). Consequently, he left the RN and is now member of the Political Commission of the PPC. In the election 2011, he was re-elected for another five-year term on the ticket of the Alliance for the Great Change, to which the Christian democrats now belong.