[gknoy]

The historical nature of soldiers of armed guards with the authority to kill you lends credence to his suggestion that it's not an unreasonable expectation to believe that they _could_ shoot you.

Local mileage and laws may vary, but erring on the side of caution when you see a soldier means that it's prudent to act as if he can legally fire upon you -- even if that assumption is not actually true at that specific time or place.