The Commercial Court of Paris founon Thursday that certain advertising claims used by McNeil Nutritionals, the marketers of the ingredient, violate French consumer protection laws.
The slogans in question are "Because it comes from sugar, sucralose tastes like sugar" and "With sucralose: Comes from sugar and tastes like sugar".
The case had been brought against French subsidiaries of US-based McNeil Nutritionals by the French subsidiary of competing sweetener firm Merisant.
The court awarded Merisant €40,000 in damages, and ordered McNeil to cease the advertising claims.
The firm now has 30 days to amend all Splenda packaging of.
In addition, the Court prohibited the distribution of any products under the trademark Splenda with unchanged packaging after a period of four months.
"We're pleased the Court held McNeil accountable for Splenda advertising that we believe has intentionally fooled a significant number of consumers into thinking Splenda contains sugar and no calories, and that it is a natural product; both are completely false," said Paul Block, chief executive officer of Merisant.
"We want to ensure fair competition through accurate advertising so that consumers can make informed decisions about the products they're buying (…)
Splenda is a synthetic compound - created in a lab and manufactured in a chemical plant - and is no more natural than any other low-calorie sweetener."
McNeil said it intends to appeal the court's decision, saying it "continues to believe in the validity of its claims".
It also said it plans to " continue to ensure its advertising represents the products in an accurate and informative manner."
Tate & Lyle, the UK-based manufacturer of Splenda, said it was "disappointed" that the court ruled in favor of Merisant.
It added: "However, Tate & Lyle was not a party to the action and it is not in dispute that our ingredient, Splenda Sucralose, is made from sugar."
The ruling came just a day before a similar case between Merisant and McNeil in the US resulted in a settlement agreement between the two firms.
Both parties agreed to make no additional comment on the terms of the settlement agreement, which was the culmination of a three-year battle between the two companies.
The long awaited court case, which began last month in the US District Court for the Eastern District of Pennsylvania, was set to determine the fate of marketing slogans used for Splenda in the country.
After several weeks of court battles, the case finally went to jury on Friday.
The confidential settlement comes as a mysterious end to a conflict hitherto kept in the public eye.
Merisant had said the case was all about providing consumers with accurate information as well as an "equal playing field" for manufacturers of other artificial sweeteners.
"We've always been very clear that Equal is an artificial sweetener.
It's about fairness in business," the firm told FoodNavigator-USA.com.
McNeil will also be facing another case for its marketing of Splenda in the US, brought by the Sugar Association and due to go to trial in November.
The case follows a long-standing dispute between the company and the trade body, which also claims the slogan used is misleading.