We should stop all the current Meth marketing...that'll solve the addiction problem for sure.

What are all these scenarios where policy makers have absolute control of how drugs are sold and consumed? Meth is illegal, as in we don't allow "marketing" today. But if it was legal, it'll only be the marketing that will be the potential problem? What is the point of these arguments? The low enforcement/legalization options have been tried in various places in various ways, not one has gone well. Besides magical thinking, what is the actual argument that legalizing drugs makes it less of a problem?

Marketing of legal prescription drugs can be restricted in certain ways, but it has to be allowed unless we modify the First Amendment. Freedom of expression is a fundamental right and can't be casually eliminated just because we don't like the results.

Is that the overwhelming opinion of legal scholars?

I think I would be just fine with a change like that. If sales of a product can be restricted, why should advertising for that product need to be unrestricted?

It doesn't feel to me like advertising is more of a fundamental right than engaging in sales.

Marketing is restricted, regulated and outright banned for a number of products and services.

Advertisements for prescription drugs are very heavily restricted in the US. And, as far as I know, companies selling prescription drugs may not encourage doctors to use them arbitrarily.

I don’t know whether anyone has ever tested the constitutionality of the relevant laws and regulations, but they exist and are enforced.