Question is, can the retailer request a non-oxygenated blend or is the distributor required by law to blend it regardless? Quite honestly I wouldn't trust the retailer's answer. I'd wager that most of them aren't even close to up to speed on the legalities of the fuel they sell and just trust that when they say "regular" they think it means. Heck, for at least a decade after unleaded was completely and totally gone at the pump, I regularly heard people say their fuel was the "old good stuff" just because the distribution salespeople and the pump labels still used "Regular" to describe the lowest octane blend.
Actually, a better source of info would be the regulatory agency in your state. They should know off the top of their head if oxygenated fuels are mandated, either statewide or by specific area. They may even have it on their web site for quick reference.
Brad