Does a Four-Part Test on Regulation of Commercial Speech Still Govern the Review of Restrictions on It ?
In Central Hudson Gas & Elec. Corp. v. Public Serv. Commn. (447 US 557, 566 ), the Court set out a four-part test for reviewing a regulation that impinges on commercial speech:
" the speech must concern lawful activity and not be misleading.
 Next, we ask whether the asserted government interest is substantial. If both inquiries yield positive answers;
 we must determine whether the regulation directly advances the governmental interest asserted;
 whether it is not more extensive than is necessary to serve that interest."
"The four parts of the Central Hudson test are not entirely discrete.
All are important and, to a certain extent, interrelated." (Greater New Orleans Broadcasting Assn. v. United States, 527 US 173, 183 .)
The test still governs the review of restrictions on commercial speech. (See, supra, at 184.)