proper attire required

We hadn't even had time to discuss just what was meant by proper attire when the first atv came up from behind but I was pretty sure I wasn't wearing it. Akira atleast had a collar and a vest - I had nothing but a battered old tshirt, some hiking pants and a camera strapped to my pack and my companion wasn't looking too much better. We knew we weren't on private property and weren't expecting a gate there so that caught us by surprise but the sign itself - Proper Attire Required - really threw us for a loop as you often don't see a dress code posted at a forest gate but given the speed of the response it was clear we were being watched and decided instead of continuing on up the creek we'd go another way so we told the driver of the second atv we would just head up the other road back up to the gap. He assured us we would be better off taking the road that actually went there but seeing as how we had come from that direction we just thanked him and headed the other way instead. Nice enough guy but we never did hear any shooting.