THE THREEFOLD LAW
The threefold law of return, also known as The Rule of Three, is a concept which is not necessarily followed by all pagans. It tends to be a Wiccan term, yet even some Wiccans question it in theory.
By the tenets of the threefold law, all energies and intents that you send out into the universe come back to you, times three. In essence, it is believed that if one sends negative energy out into the world, that same negative energy will return to them, three times as strong. Likewise, any positive energy sent out will be rewarded threefold. Therefore, most Wiccans make a concerted effort not to direct negative energies or intentions under any circumstances.
Rather than attacking an enemy, they do spells for thier own safety and protection. Rather than seeking revenge, they ask that justice be served. By handling things this way, they believe that it is up to the God, the Goddess, and the elements to determine the course of these matters.
The basic underlying theme, as is also true with The Wiccan Rede, is that all things should be done for the good of all, and should harm none.
Many witches and other pagans do not subscribe to the Rule of Three because they feel that it is punitive in nature, and seems to contradict the basic theme of balance which is foundational in most earth-based religions. Most pagans believe in some form of karma, but may not feel that the karmic backlash is amplified by three.