The only armed force the Union government controls, Peacemakers are used to settle squabbles between guilds, hunt criminals, and settle disputes where mercenaries are not practical or possible.
As a requirement for Union membership, a planet must send a set number of individuals (based on population) to participate in the Peacemaker Guild. No more are accepted, to keep any race from dominating. Leadership of the guild is rotated every five years, and selection is random.
Any race who signs on as either a full member or an associate member of the Galactic Union grants complete and unlimited access to their world to any Peacemaker, including their deputies and any items they can carry on themselves.