Quote of the Day - I like C-SPAN because I like getting news that isn't filtered.
PuriTec sells water filtration devices throughout the world from its headquarters in Nevada, and mainly so through its website. PuriTec, not surprisingly, sells its filters in California, too. In its website advertisements, PuriTec claimed that its filters removed or reduced organic, inorganic or microbiological contaminants.
California has two statutes that require water filter companies to submit their filters to the Department of Health Services for certification that the filters live up to these claims.
Prior to 2003, PuriTec had not submitted certain filters to the DHS for certification, but nonetheless advertised those filters on its website, advertising the claims regulated by statute. When DHS found out, it issued a Notice of Violation to PuriTec, and in response, PuriTec said it would remove the claims from its website. In the words of the court of appeal, over the following year PuriTec "assured DHS that it would change its website to comply with California law, but it dragged its feet along the way."
DHS wasn't happy about the foot-dragging, and sued PuriTec to gain compliance.
PuriTec defended the lawsuit, and drug up the defense of the "dormant commerce clause," which is shorthand for saying a state cannot legislate requirements that interfere with interstate commerce. PuriTec essentially claimed that California's regulations created a burden on its ability to sell its products throughout the country. It said California's regulations discriminated in favor of filter companies in California and the benefit of the certification process did not outweigh the burdens on its sales.
The Court quickly dealt with PuriTec's claims, ruling that in-state companies were regulated in the same manner as out-of-state companies, and Californians (as well as residents of other states, presumably) benefited substantially from the DHS' efforts to make sure PuriTec's products lived up to its advertising claims.
The Court's opinion caused PuriTec to create a separate website for California residents, where its products are certified by the state as compliant with its advertisements. PuriTec has another website for everyone else, presumably listing filters not certified for sale in California.
You can decide which site you want to buy products from.