Massachusetts provides special admission rules for government attorneys licensed in other jurisdictions under the Massachusetts House Counsel Rules.
Massachusetts also provides a Massachusetts Multijurisdictional Practice Rule (MJP) within its rules of professional conduct. Comment 16 to that rule provides an interpretation that exempts government attorneys from the unauthorized practice of law.
Please also see the Massachusetts Bar Reciprocity page to view the qualifications for Admission on Motion, and the Massachusetts Pro Hac Vice page to view the requirements for admission to a particular proceeding.