Can Active-Duty Military Members Attend Protests or Campaign Rallies?
According to military law experts, DoD Directive 1344.10 dictates whether active-duty military members can participate in political activities, including protests and rallies.
That directive, they say, does allow military members to personally engage in partisan activities, including writing letters to the editor for or against a specific candidate or attending events as spectators out of uniform.
But it blocks them from leading or actively participating in those events, publishing partisan political statements outside of a letter to the editor, speaking at any political gathering or soliciting votes.
https://www.military.com/benefits/military-legal-matters/active-duty-military-participate-protests-make-political-statements.html