Re: USA
He's wrong. Not only is it a federal matter, it's already illegal.
It's just that the FTC hasn't bothered enforcing it.
"It shall be unlawful for any person, partnership, or corporation to disseminate, or cause to be disseminated, any false advertisement—"
"(2) By any means, for the purpose of inducing, or which is likely to induce, directly or indirectly, the purchase in or having an effect upon commerce, of food, drugs, devices, services, or cosmetics."
"(b) Unfair or deceptive act or practice
The dissemination or the causing to be disseminated of any false advertisement within the provisions of subsection (a) of this section shall be an unfair or deceptive act or practice in or affecting commerce within the meaning of section 45 of this title."
"(1) The term “false advertisement” means an advertisement, other than labeling, which is misleading in a material respect; and in determining whether any advertisement is misleading, there shall be taken into account (among other things) not only representations made or suggested by statement, word, design, device, sound, or any combination thereof, but also the extent to which the advertisement fails to reveal facts material in the light of such representations or material with respect to consequences which may result from the use of the commodity to which the advertisement relates under the conditions prescribed in said advertisement, or under such conditions as are customary or usual. "
https://www.law.cornell.edu/uscode/text/15/52#a
"(a) Imposition of penalties
Any person, partnership, or corporation who violates any provision of section 52(a) of this title shall, if the use of the commodity advertised may be injurious to health because of results from such use under the conditions prescribed in the advertisement thereof, or under such conditions as are customary or usual, or if such violation is with intent to defraud or mislead, be guilty of a misdemeanor, and upon conviction shall be punished by a fine of not more than $5,000 or by imprisonment for not more than six months, or by both such fine and imprisonment; except that if the conviction is for a violation committed after a first conviction of such person, partnership, or corporation, for any violation of such section, punishment shall be by a fine of not more than $10,000 or by imprisonment for not more than one year, or by both such fine and imprisonment"
https://www.law.cornell.edu/uscode/text/15/54