I think laughter would be the best medicine in an encounter of this type. I could not keep from bursting out laughing anyway, and for sure would not act elusive, angry, or otherwise suspicious.
That approach worked for me when last dealing with armed gov agents, at the INEL nuke test site in the SE Idaho desert. I flew over at a legal height, and noticed flashing lighted vehicles below seemingly following my flight path (40 mph cruise, it wasn't hard to keep up, back in the ultralight days). When I left the site boundary's I got low enough and parallel to the road to make eye contact with the guys in the vehicles, and when they made the "land right now motion", I did, in a more or less clear of sagebrush area. They came out with guns drawn and I started laughing out loud, while putting my hands up and asking them not to shoot. They responded in kind, laughed that is, and the situation quickly cooled off. I did however make a very firm point of my known altitude over the Site, and I had just set my altimeter in Howe so felt I had my ass covered. They agreed, thanked me for my cooperation and we parted ways.
This was late '80's but I'd still laugh in their faces today, partially to defuse the situation, but mostly because i find it hilarious they would be wasting their resources on me and my experimental aircraft. They could search, no problem, if they started taking inspection panels off without my permission or other wise messing with HONEY, I'd quite laughing I guess.
