"and man shall have dominion over the Earth and all it's creatures"
I'm paraphrasing, but you get the gist.
"shall not kill" was intended toward a fellow man, not animals.
I find that most ministers and priests have no objection to hunting and a surprising number hunt themselves. My uncle is an ordained minister and has done much hunting and packs a concealed weapon quite a bit.
I'm somewhat surprised at the nuns behavior on this one.