U.S. service members are sworn to protect against enemies foreign and domestic, and must wear their uniform in the performance of official duties.
I believe 18 USC 930 (d)(1 and 2) should include all on-duty personnel allowing them to carry a sidearm (gov't OR personal) provided the weapon/ammunition complies with Geneva convention policy, and does not induce unnecessary suffering should the weapon be used to lawfully protect personnel or property of the United States.
Personnel must already comply with the Lautenberg Amendment or risk discharge and a commander may relieve a service member of their personal firearm at any time for perceived mental distress or treatment. My petition gives options of protection against loss of life if the Ft. Hood and Navy Shipyard incidents happen again.