The federal government? Well, the federal government has the power to regulate commerce among the several states, and "to regulate" includes "to prohibit". Or so the U.S. Supreme Court says:
"Congress can certainly regulate interstate commerce to the extent of forbidding and punishing the use of such commerce as an agency to promote immorality, dishonesty, or the spread of any evil or harm to the people of other States from the State of origin."
-- Brooks v. US, 267 U.S. 432 (1925)
"In fact in the 1920s they had to pass an ammendment to ban alcohol ..."
Yes, an amendment was passed. But it was desired, not required.
"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."
-- www.druglibrary.org/schaffer/history/rnp/RNP1.html
"... and it was repealed."
Yes. Section 1 of the 21st amendment repealed the 18th amendment. That returned everything to where it was.
But then Section 2 was added, removing the power to regulate alcohol from the federal government and returning that power exclusively to the states.
"It cannot limit the rights of the people, because our freedom doesn't come from the Constitution, its ours with birth."
The Constitution protects your freedom of speech, but it is limited -- it is illegal to libel or slander someone, for example, or yell "Fire" in a crowded theater. Congress may reasonably regulate your constitutionally protected rights.