For information re a legal career in USCG JAG go to uscg.mil/legal/recruit. A number of links will direct you to requirements--physical and academic--and the process of entering the direct commissioning program.
Re the AUX google USCG AUX for a unit near you and contact that unit. Prior response concerning joining the Auxiliary I believe answers your query.
Clearly JAG offers a career in legal work whereas the AUX legal concerns itself with internal administrative work more than day to day legal work.