Missouri provides special admission rules for government attorneys licensed in other jurisdictions under the Missouri House Counsel Rules.
Missouri also provides a Missouri Multijurisdictional Practice Rule (MJP) within its rules of professional conduct. The Comments to MJP Rule 4-5(c)(4) and (d) provide an interpretation that exempts government attorneys from the unauthorized practice of law.
Please also see the Missouri Bar Reciprocity page to view the qualifications for Admission on Motion, and the Missouri Pro Hac Vice page to view the requirements for admission to a particular proceeding.