I'm not sure if you have made this mistake, but I think this is a mistake that many of us have made. Perhaps you were prescribed a controlled substance and someone you know, perhaps even love, is having terrible pain and they ask you for a pill to help them out and you give it to them! They may have the same prescription, but just do not have it with them. It sure can make us feel better that we helped someone get relief faster!
What just happened, if you are in the US, is you just broke the law. The person taking the pill just broke the law too.
Someone I know has recently found out the difficult way that this practice is illegal. We're not sure of the legal ramification of this mistake yet, or if there will be one, but I'm hoping no jail time and that it will not change the course of this person's life.
I would ask that you share this with anyone that you know that may commonly try to help other's out and is not realizing that it is illegal. I would hate for anyone else to go through the troubles that the person I know is going through.