Commercial speech is protected by the First Amendment. Regulations of commercial speech need to pass the "Central Hudson Test", which requires a compelling government interest (subject to heightened scrutiny) and narrowly-tailored regulation. Under this rubric, you can get cigarette ads off billboards, but you probably can't regulate Nike's ads.
>>tptace+(OP)
If SCOTUS can develop a test to determine when the government is allowed to violate 1A, then they can loosen that test's requirements. They won't, of course, but I don't see why they couldn't, if they wanted to.