Individual liberty and Personal responsibility.
Life, liberty and the pursuit of happiness.
No Nannystate.
There are more.
This pits personal liberty against personal responsibility.
You may be extremely responsible. But if you take a decision altering drug, which alcohol, cocaine, marijuana and other drugs are, then you will most likely do things that you otherwise would not do, and lose control over functions wyou would normally have under control.
PUBLIC SAFETY demands that these things be regulated. The argument is not to deny you of liberty, it is to exercise responsibility required for public safety.