What is a no-soliciting ordinance?
A local rule limiting door-to-door sales — usually a permit requirement, allowed hours, and a duty to honor posted no-soliciting signs.
Most door-to-door restrictions are municipal, not federal. A city or county typically requires a solicitor’s permit, sets the hours knocking is allowed, and makes it an offense to ignore a posted no-soliciting sign or a registry of addresses that opted out.
The rules are genuinely local, so a crew working three towns in a week may face three different sets. Permits are usually cheap and quick, sometimes per rep and sometimes per company, and enforcement often arrives as a police call from an irritated resident rather than a citation.
The commercial reason to care is not the fine. It is that a complaint call travels through a neighborhood faster than any pitch, and a company known for ignoring signs loses the street. Skipping posted houses costs almost nothing and protects the ones you do knock.
None of this is legal advice — check the rules for the specific city you are working, because they change and they are rarely posted where you would expect.