Consider this scenario. You would never traffic in illegal drugs, but your brother does not have health insurance, and he is in serious pain from a recent back injury. You have almost a full bottle of Vicodin leftover from your last trip to the dentist, so you are considering sending them his way. You know it is not legal to give him your medication, but you figure the risk that anybody will find out is almost nil.
Do not do it. Both federal and local authorities have increasingly focused on stopping the transportation of illegal drugs through the mail. For various reasons, a significant portion of the illegal drug trade has moved online, and large amounts of illegal drugs end up being shipped through the United States Postal Service (USPS).
You may be thinking, “But my mail is private?” That is mostly true. The post office generally cannot open your mail and packages and nose around just because they are so inclined. However, the federal government has thrown increasing numbers of resources into stopping illegal drugs from going through the mail. This includes the use of drug-sniffing dogs. All it takes is an alert by one of these canines, and the postal service authorities can obtain a warrant to open your package.
The canines may not be actively looking at your package. They may be there to try to spot drugs being moved into the United States from overseas, but it does not matter if you are caught. You would still face felony-level drug charges.
If you do make a mistake, do not let drug charges ruin your future. Find a knowledgeable defense attorney who can help protect your interests in court.