Buddhism wasnt meant to be a collection of strict rules for mind-control like many organized religions.

Buddhism is all about your body they may have used to smoke or used marijuana for rituals way back but now that they know it harms your body it would deffinetly have changed to somthing they do not accept.
Its not all about body, some Buddhists may practice things like yoga as a way to shape both their body and mind, others practice methods of meditation, some use drugs, the minority of buddhists worship any sort of god. Cannabis is one of the safest substances known to man, there are no records of death caused by marijuana in the thousands of years it has been used. They havn't even been able to give any real evidence suggesting use of cannabis leads to lung or brain damage.

The five precepts of Buddhism are:
1. Abstain from killing living beings;
2. Abstain from taking that which not given;
3. Abstain from sexual misconduct;
4. Abstain from false speech;
5. Abstain from distilled substances that confuse the mind. (Alcohol and Drugs)

The underlying principle is non-exploitation of yourself or others. The precepts are the foundation of all Buddhist training. With a developed ethical base, much of the emotional conflict and stress that we experience is resolved, allowing commitment and more conscious choice. Free choice and intention is important. It is "I undertake" not 'Thou Shalt". Choice, not command.
There are many Buddhist who use a wide range of drugs for mind expansion and as part of their lifestyle.