After 120 years, the long relationship between regional bottler Dublin Dr Pepper and the Dr Pepper parent company has hit a sour note, the Christian Science Monitor reports.

The Dublin Dr Pepper Bottling Company — founded in Dublin, Texas, in 1891 — is the world's oldest Dr Pepper bottler. It represents a small territory — a mere six counties — and the soda bottled there differs in two ways from the national brand: it is made with real cane sugar instead of high-fructose corn syrup and it is marketed as "Dublin Dr Pepper."

Dr Pepper Snapple Group, the bottling giant spun off from Cadbury in 2008, now says that Dublin Dr Pepper is violating the Dr Pepper trademark and the two companies' long-standing agreements by marketing and selling its product outside of the approved six-county territory. The parent company has filed a lawsuit to end both of those practices, and also seeks attorney fees.

In a statement, Dublin Dr Pepper attorney Steven Wolens said that attorney fees alone would cripple the company. "There would be nothing left except the bottle caps," he said.

In an email to the Los Angeles Times, Dr Pepper Snapple Group explained the reasoning behind the lawsuit: "Quite simply, the Dublin bottler is misusing our trademark and has been for years. We're not seeking money or to prevent them from selling Dr Pepper made with cane sugar. We simply want them to sell only within their six-county territory and stop marketing and packaging Dr Pepper as 'Dublin Dr Pepper.'" Dr Pepper Snapple says that the existence of Dublin Dr Pepper dilutes the Dr Pepper trademark and creates confusion in the marketplace.

According to the Fort Worth Star-Telegram, Dr Pepper Snapple filed its lawsuit on June 28, after "Dublin Dr Pepper refused to stop shipping beyond its territory or give up its logo" unless it was financially compensated, a detail neither side is elaborating upon.

"We tried to resolve these issues with Dublin without turning to the courts," said the Dr Pepper Snapple press statement, saying it offered the local company "alternative packaging" which "stays true" to the national grand. "They refused this compromise and demanded money to honor their agreement, which left us no choice but to file suit."

Some observers have wondered if the suit is less about trademarks and more about sugar. Last summer, for the brand's 125th anniversary, Dr Pepper Snapple experimented with selling soda made with "real sugar" instead of high-fructose corn syrup. (Kosher-for-Passover Coca-Cola is another example of a soda switching its formula from corn syrup to sugar.)

Dubliners take their Dr Pepper seriously. Every year, the town is renamed Dr Pepper, Texas, for one week. There is also a museum devoted to the homegrown drink, a wide range of Dublin Dr Pepper merchandise, and even a series of BBQ sauces. The town citizens held rallies last month in support of their local company.

The Dr Pepper drink was invented in 1885 in Waco. Dr Pepper Snapple is based in Plano, Texas.