Days before the national “do-not-call” lists were scheduled to take effect, a federal court has blocked the lists, designed to restrict telemarketers from making unwanted sales calls.

The ruling Tuesday by the U.S. District Court in Oklahoma was a victory for the Direct Marketing Association, a trade group representing about 5,000 U.S. companies and telemarketers who said the registry violated their rights under the First and Fifth Amendments to the Constitution.

However, the judge did not rule on the grounds of free speech violation, instead ruling Congress had not given authority to the Federal Trade Commission to establish the national registry.

U.S. District Judge Lee West said the FTC cannot enforce the do-not-call registry. The FTC signed up 50 million phone numbers for the list, which was due to go into effect October 1. Under federal rules, telemarketers could be heavily fined for calling numbers on the list.

“The DMA was arguing First Amendment rights, saying that various groups — such as Jehovah’s Witnesses, Girl Scouts and neighbors — can call up a person in their home, but telemarketers cannot,” said Barbara Mack, associate professor of journalism and communication.”But it doesn’t appear the judge ruled on First Amendment grounds at all.”

Telemarketing companies will retain their right to call people on the registry, but some telemarketers said the court ruling will have very little impact on their business.

Mark Drish, executive vice president of Cedar Rapids-based telemarketing company Access Direct, said the do-not-call list never threatened to change his business. The company operates an Ames branch, located at 215 Alexander Avenue.

“The list provided broad exemptions and our company falls under most of those,” Drish said. “To be honest with you, the do-not-call list wasn’t going to have an impact on us.”

He said most people believed the do-not-call list would stop all telemarketing, but this idea was false.

“For example, your cable, credit card and phone company can continue to call you,” Drish said. “There were many people exempt from the do-not-call lists, and our company was one of those groups. Even if it did take effect, the list wasn’t going to have the impact I think everyone was counting on.”

ISU students had mixed reactions over the court decision. Stefan Knudsen, sophomore in agriculture education, disliked the decision but understood the DMA’s reasoning.

“I’m not sure how I feel on this issue,” he said. “On one hand I hate being bothered by telemarketers, but on the other hand, I don’t see how we can silence one part of society while allowing everyone else to speak.”

—The Associated Press contributed to this article.