This is a good way to put it. It also holds to Locke. He basically said that, for instance, if someone tries to kill you,violating your natural right to self ownership, they have forfeited the same right for themself and it is legitimate to defend yourself up to killing the attacker.
Rothbard defined his ideas of law on this principle. He argues that if someone kills someone they could be killed, but that it may be better for the next of kin, who needs to be made whole, for them to work out another way with the murderer, such as laboring for a particular time and for a particular ammount of money. What Rothbard points out is that it is the person wronged that must be made whole, not the community and certainly not the government.
The key word in the NAP is aggression. Don't go starting shit, but there is nothing wrong with finishing it. My dad taught me that when I was like five. Seems pretty easy.
RE: the NAP and the judo flip