In 2006, there was a challenge posed to this standard and to other standards for U.S. food products. The Grocery Manufacturers Association, the trade group representing the food, beverage and consumer products industry, petitioned the FDA to "modernize" its regulations.
GMA spokesman Brian Kennedy said that the goal of the petition was to accommodate innovation in the food industry.
He said that under current regulations, for instance, if food companies make pasta out of a blend of whole wheat flour and white flour, they can't officially call it "pasta."
A blended product, he said, would probably be more palatable to consumers than 100 percent whole wheat pasta. But if the new product isn't called pasta, he said, people won't buy it.
"When they want to have pasta, they want to purchase something that actually says pasta," Kennedy said.
But when the GMA petition came to light, it was its implications for chocolate that got attention: An appendix to the petition noted that the changes could allow for manufacturers to use vegetable oils other than cocoa butter to make chocolate.
Both consumers and small chocolatiers decried the proposed changes. In 2007, Mars Inc., the No. 2 chocolate-seller in the U.S. and the maker of M&M's, broke ranks with industry peers and also came out against the petition.
Europe has had its own chocolate wars. In 2000, after years of heated debate, the European Union struck an agreement allowing for chocolate products to contain up to five percent of oils other than cocoa butter.
To date, the U.S. petition has gone nowhere.
"FDA will complete the review of this petition in context of the Center's priorities," FDA spokesman Mike Herndon said in an e-mail to ABCNews.com.
Meanwhile, May said that candymakers can skirt the regulations for what can be labeled chocolate by emblazoning their wrappers with phrases like "chocolatey," "made with chocolate" and "chocolate candy."
Hershey's Kissables, she said, are one example. May, who blogged about Kissables earlier this month, said that when the candy contained cocoa butter, the candy's wrapper included the phrase "milk chocolate." It's since been replaced with "chocolate candy."
On the back of the Kissables wrapper, the vegetable oils used are listed as "palm, shea, sunflower, and/or safflower oil."