The following is excerpted from a document, "US Marines In Lebanon 1982 - 1984", that is posted on the Marines dot mil website:
"Eucom [United States European Command] peacetime rules of engagement dictated that the Marines were to carry unloaded weapons, although it does not take long to insert a magazine into a weapon and chamber a round. The rules also dictated that the on-the-scene commander had the right to determine what the appropriate response would be if there was a hostile act committed against Marines…. As far as Colonel Mead was concerned, the Marines were “…comfortable with our rules of engagement, which had been kept simple and therefore readily understandable”
Given how notoriously hands-off Reagan was on policy details, do you HONESTLY believe he was defining for the Marines whether the weapons they carried were permitted to be loaded or not?