The thing with laws is, again, they are just our interpretations of how we think things work. The actual way things work may be written in stone, but our interpretations, even if we call them laws, are just that. They are things which we have observed to be true in every known circumstance. As far as we know, we could be 5 minutes away from seeing an exception to a law, but we don't know about it until we see it.
I highly doubt that a sniper rifle bullet is going to go setting of an atomic reaction...
I think you're overestimating the progress of human armor. We're using ceramic, fabric, and some metal plating to protect our soldiers. Full-body armor is unheard of. To be honest, medieval armor offered better protection in many ways than the modern equivalent. Of course, that's because our armor technology actually slipped backwards for awhile when mass-produced firearms became the mainstay and personal metal suits were far too costly to implement in the numbers required for an effective armored infantry force. Hell, modern military helmets are Kevlar. This stuff is what our weapons are currently gauged against; alien armor tech could easily make use of stronger synthetic fibers (carbon nanotubes, like their light armor), high-density metals, layers of breakable (force dispersing) plates, other reactive methods. This whole atomic bond thing is getting a bit off topic, and giving our own armor technology way too much credit for the crap it is.
