The principle of Self Ownership, which is the basis of the philosophy of liberty
https://www.youtube.com/watch?v=M9srplWe_QQ
It would not be murder to protect your own life from the aggression of others. However any use of violence must be in proportion to the threat to your life. I.e I do not believe you have the right to kill someone for trespassing, but only in those circumstance where there is a reasonable believe your life to be direct and immediate danger.