Speech proposing a commercial transaction is protected, though less robustly than other expression.
The threshold. The speech must concern lawful activity and not be misleading. False or misleading commercial speech may be prohibited outright.
Intermediate scrutiny. The asserted government interest must be substantial; the regulation must directly advance that interest; and it must not be more extensive than necessary, requiring a reasonable fit between means and ends.
Direct advancement requires evidence. Speculation and conjecture do not satisfy it, and regulations invalidated at this step are usually invalidated for lack of a record.
Compelled commercial disclosure is assessed under a more permissive standard where the required disclosure is of purely factual and uncontroversial information, is reasonably related to a substantial interest, and is not unduly burdensome.
Professional speech. There is no separate reduced-protection category for speech by professionals as such, though regulation of professional conduct that incidentally involves speech remains permissible.
Where municipalities encounter it. Sign ordinances, on-premises advertising, solicitation and canvassing rules, licensing conditions restricting advertising, and restrictions on particular industries.
Drafting guidance. Build an evidentiary record before adoption, target the identified harm, and prefer disclosure requirements to prohibitions.