The non-aggression principle is an ethical stance which asserts that "aggression" is inherently illegitimate. "Aggression" is defined as the "initiation" of physical force against persons or property, the threat of such, or fraud upon persons or their property. In contrast to pacifism, the non-aggression principle does not preclude violent self-defense. The principle is a deontological (or rule-based) ethical stance.
I see some serious problems with this principal.
One is that it doesn't seem to recognize the reality that the concept of owning property is, itself, an act of aggression. And since this non-aggression principal allows for the aggressive defense of property, it is essentially contradicting itself.
Property is nothing more then that which I declare to be "mine", and intend to defend by force. (Sounds a lot like taxation, does't it?) Thus, the concept of owning property, when applied to reality, is by it's nature aggressive.
Secondly, how can we enforce this non-aggression policy without the use of force (which I presume you see as aggression)? Because without enforcement, the ideal cannot become a reality. It remains just an ideal. In fact, proposing it as a policy would require that we contradict it as an ideal.
And finally, how does this ideal account for innate human aggressiveness and competitiveness? We humans would have to be something other than what we are, to be able or even willing to employ such an ideal. And we aren't something other than what we are. We are what we are and we will remain so.