"An amendment to the Constitution obviously appealed to temperance reformers more than a federal statute banning liquor. A simple congressional majority could adopt a statute but, with the shift of a relatively few votes, could likewise topple one. Drys feared that an ordinary law would be in constant danger of being overturned owing to pressure from liquor industry interests or the growing population of liquor-using immigrants. A constitutional amendment, on the other hand, though more difficult to achieve, would be impervious to change. Their reform would not only have been adopted, the Anti-Saloon League reasoned, but would be protected from future human weakness and backsliding."
-- druglibrary.org/schaffer/history/rnp/RNP1.html
Now, if you have information supporting your statement that a constitutional amendment was required, I would (seriously) be interested in reading it.
Since the courts have shown 70 years of gutlessness, it is time to ammend the Interstate Commerce Clause and limit it to its original purpose.
So9
If you have any information about the author's constitutional basis for the claim that it did not, I would (seriously) be interested in reading it.