Be in no doubt. If the military guard believed that he was following lawful orders in doing so, he would shoot the reporter.
David New was a soldier who refused to wear UN insignia on his US Army uniform because he believed that the order was unlawful (expecting him to wear a uniform which represented allegiance to the UN ). He was court-martialed and found guilty of disobeying a lawful order. I believe that his case is nearing the US Supreme Court.
The expectation that soldiers will guard access to a battle zone is lawful. The soldier would have fired.