The US-DEA decided to let marijuana remain a "Schedule 1" substance meaning its effect has no beneficial medical value. Essentially poison.
They admit it has an effect though. Whether that effect is beneficial is a complicated subject under heavy debate. In this day and age, they know it's safe. They own the patent, after all (#patent6630507). Objectively it has been shown to be therapeutic for individuals with epilepsy and autism to muscular dystrophy and PTSD. It has shown in study to kill cancer cells specifically opposed to the "shotgun" technique of chemotherapy actually shrinking tumors to nothing, as confirmed by The American Cancer Society. It has offered an improved lifestyle for many people in countless ways. Google "CBD" for yourself and see. Cannabis has been a part of human culture for 10,000+ years. Every person has what is called an endocannabinoid system running through their body that recognizes the constituents of cannabis and therefore nourishes us. Our bodies know what it is already. Only in the 20th Century did it come into question. It has to make you wonder.