The 3 fold law is a scam. It's made up by those who want to control us. They know black magick is powerful and can punish wrongdoers, so they invented a scammy "3 fold law" to scare people from using it.
Nothing bad will happen when using black magick, if you do it correctly. The only way it can backfire is if you do it wrong, such as if you take in the negative energy inside yourself instead of visualizing it outside, or you feel any guilt or regret for using a black magick spell or if you can't focus one-pointedly on directing the energy to your victim and your mind wanders so you end up directing some of that energy to yourself. Most people clean their auras after a black magick working to remove any lingering negative energy for extra safety.
But yeah, don't be fooled by wiccan bullshit like "three fold law". Everything Wiccans and "white lighters" say is wrong. Wicca is a scam. Most of what you read about magick, occult and spells in mainstream sites/books is wrong, in fact. The same people slander our Demons and believe they are evil beings who must be controlled with circles, but it's the opposite: if you use circles when summoning Demons or try to control them is guaranteed to make them angry, it's better to treat them with respect.