Prohibiting alcohol would require an amendment to the constitution.
Realize that the Supreme Court has interpreted the federal government's constitutional powers much more broadly in the decades since prohibition.
This petition was in direct response to the DEA's recent refusal to remove it from Schedule I status. This keeps it in the same class of drugs as heroin and cocaine.
It was an abject failure.
This is not about "letting people get loaded". That will always happen. This is about taking away what could be considered the primary tool of tyranny by the State. Now the War on Terror is edging it out for first place.