I've said it before and I'll say it again - the Three-fold "Law" is a big fat serious lie.
I don't have to go digging up archaic historical references or try to mis-apply laws of physics to justify that statement, either. Look at your own lives and the people you've known. How many people who have died of cancer actually deserved such a painful, horrible death? How many folks who gleefully run around giving others the shaft and stabbing people in the back have financial success and have a whole lot of fun? How many people in the 9/11 attacks might have had the "bad karma" that meant they deserved that death?
Do I believe that what we put out we get back? Yes. Just not 3 times. Do I believe that Deity punishes people according to our moral guidelines? Nope. The gods have their own rules, and they aren't sharing what they are.
Personally, I think Gerald Gardner and Doreen Valiente made the 3-fold "law" up in an effort to keep people from running around hexing everyone willy-nilly. While I understand that it may have been for "the greater good", I also question whether they should have been teaching magic to people they didn't trust to use it wisely? Maybe for the time period, it was the prudent thing to do, but do we really need those kind of training wheels anymore?
I think the "Rule of Three" has itself caused harm. There are all sorts of people who won't even cast a healing spell for someone in a coma because it might "interfere with their free will". Poppycock. If someone is meant to die, or stay in a persistent vegetative state, or even have a really bad case of the flu, then my attempts at healing them won't make a bit of difference. If, however, the sick person is presented to me as an opportunity to help someone and I don't try to help them for fear of negative repercussions (which many are), then what kind of witch am I? Personally I think if you don't help, you don't deserve to call yourself a witch. I know we can't help everyone because trying to do that would burn us out completely, but a wise witch listens to their intuition and knows when and when not to try to help, and doesn't live in fear of backlash.
So yes, I'm saying it publicly - go ahead and cast healing spells. Cast fertility spells for friends who are trying to have a baby (as long as they're not also doing fertility treatments, or they could wind up with triplets or more). Cast a curse on people who are raping, robbing, and otherwise causing harm. You might help save lives that way. Have the cojones to be a witch, for goodness' sake.