Article I, Section 8, the Necessary and Proper Clause. Since Congress has the constitutional authority to prohibit the commerce of certain drugs, the Necessary and Proper Clause provides Congress with the federal power to enforce those restrictions. How else?
The same is used to justify the FBI, BATF, IRS, etc.
Article I, Section 8, the Necessary and Proper Clause.
The Necessary and Proper Clause cannot stretch the Commerce Clause, which is carefully worded to exclude intrastate commerce, into including intrastate commerce.