Can TCBY say they are "The Country's Best Yogurt"? Can an cider mill ask " How do we Make the Best Apple Cider in West Michigan?" (Quoting from http://www.klackleorchards.com/make-best-apple-cider-west-mi... ). Team Razer says they "make the best gaming peripherals in the world" (http://www.razerzone.com/team/join ) and Surefoot makes "the best fitting, best performing ski boots in the world" (http://www.surefoot.com/news.php ).

The answer is "yes." Under US law, these are "harmless puffery."

A search, btw, finds that SUNOCO is "the most environmentally-friendly company in the entire [petroleum] industry" http://prezi.com/2m6blwsr9u9c/geo-greenwash-ad/ and Sediment Removal Solutions is "the most environmentally friendly company around" http://www.sedimentremovalsolutions.com/franchise.html .

At some point there may be problems, but as there's no standard for 'environmentally friendly', the claim is rather vague in the first place. Still, see Kasky v. Nike (http://reclaimdemocracy.org/nike/ ) for the question of if a company's press statements, in this case about Nike's non-use of sweat shop labor, counts a protected free speech.