The scripture verses that I think refer to the principle for government and also for the protection of life are:
Genesis 9:5-6
"And for your lifeblood I will surely demand an accounting...And from each man, too, I will demand an accounting of his fellow man. Whoever sheds the blood of man, by man shall his blood be shed; for in the image of God has God made man."
In this case it only worked one way, with Paul Hill being executed by the government. In the case of the killing of the unborn children, the government's position is opposite that of God's position. Who is going to stop the genocide and get justice for the babies killed?
Certainly not people who take the law into their own hands like Hill!