https://www.military.com/daily-news/2018/12/27/air-force-nothing-improper-airmens-pro-trump-merchandise-ramstein.html?utm_medium=Social&utm_source=Twitter#Echobox=1545952636
STUTTGART, Germany -- U.S. Air Forces Europe said troops holding "Make America Great Again" hats during President Donald Trump's visit Thursday to Ramstein Air Base were not in violation of military rules that prohibit taking part in partisan activities while in uniform.
"There is no rule against Airmen bringing personal items to be signed by the president," USAFE said in a statement.