New York ? A judge struck down a New York City rule Tuesday that required fast-food restaurants to post calorie counts on their menus, but he suggested that expanding the rule to include more restaurants could make it legal.

U.S. District Judge Richard J. Holwell said he determined the rule conflicted with federal law. Businesses had claimed that their First Amendment rights were violated by the rule, described as the first of its kind in the nation, but Holwell said he reached his decision without needing to address those claims.

The city had targeted national fast-food chains by applying the law to those that served standardized portion sizes and were already making calorie information available voluntarily.

Holwell said the city rule conflicted with federal law, which already described how restaurants should post nutritional information if they chose to do so. He said the city rule would not seem to conflict with federal law if it were mandatory both for restaurants that had posted nutritional information and for those that had not.

The Department of Health and Mental Hygiene, which proposed the rule, said the city was considering options.

“The actions of these restaurants will deprive consumers of important information for a few months, but we are confident that calorie labeling can be legally mandated by the city and will help New Yorkers be better informed and make healthier choices,” department spokeswoman Sara Markt said.