A man’s home is his castle, so the saying goes, but an unfolding First Amendment fight may determine whether the right to privacy at home is so sacrosanct that automated telephone calls about the pressing political issues of the moment can be banned.

A federal judge in Indiana came down this week on the side of domestic tranquility, but the political groups who have been stymied are promising to keep up the battle for the First Amendment right to send uninvited “robo-calls” to voters.

In the legal crosshairs are two political organizations trying to sway votes in advance of the November election. One, the Economic Freedom Fund, is backed by Republicans. The other, American Family Voices, is funded by Democrats and labor unions.

Last month, Indiana’s attorney general, Steve Carter, sued both groups for violating a 1988 state law by sending recorded calls to residents of an Indiana congressional district where a hard-fought campaign is under way. A similar federal law passed in 1991 created an exemption for noncommercial calls, such as those from charities, pollsters, and political groups, but Indiana’s statute on recorded calls does not have such an exemption.

Both groups suspended the calls, but American Family Voices and the marketing firm placing the calls for the Economic Freedom Fund, FreeEats.com Inc., went to federal court for an injunction blocking the state law as unconstitutional.

“We view this as a serious situation,” the president of FreeEats.com, Gabriel Joseph III, said.

However, the federal judge who examined the question, Larry McKinney, saw no constitutional problem with restricting the automated calls. “The statute is narrowly tailored to achieve the interest of protecting residential privacy,” Judge McKinney wrote. He said it was a so-called time, place, and manner regulation, which left “ample” alternatives open to would-be makers of unsolicited, recorded calls. “The statute leaves room for other forms of political speech such as door-to-door campaigning, bulk mailings, leafleting, and use of posters and signs to name a few,” the judge wrote. Judge McKinney said FreeEats.com also was free to use live operators to make the calls, but the company said that was impractical because it would take too long and be prohibitively expensive. Mr. Joseph said the judge gave short shrift to the free speech issues at stake. “We feel that those who look closely at the document who support free speech should be chilled,” he said.

An attorney for American Family Voices, Joseph Sandler, said the decision undermined the protection usually given to political speech. “It seems to us it’s offensive to the First Amendment,” he said. “We’re not selling anything. We’re not asking for money. We’re just speaking.”

A professor who studies First Amendment issues at the University of California Los Angeles, Eugene Volokh, also criticized the ruling. “It seems to me that this decision is assailable and is probably wrong,” the professor said.

Mr. Volokh said the decision was “plausible” under current jurisprudence, but he said the judge failed to account for a 1943 Supreme Court decision striking down an ordinance against door-to-door leafleting. In that case, Martin v. City of Struthers, the court said Jehovah’s Witnesses could not be prevented from visiting homes uninvited. “I think there’s a very close analogy,” Mr. Volokh said.

He said the constitutional problem is that some people are willing to receive unsolicited automated calls, but placing such calls is illegal under the Indiana law.

The professor also said the judge’s decision gave short shrift to FreeEats.com’s complaint about the expense of live calls. “The cost of expression is important,” he said.

A spokesman for the Indiana attorney general, Staci Schneider, said automated calls were more problematic because residents couldn’t ask not to be called back again. “You don’t have the opportunity to say no,” she said.

Mr. Joseph said his firm is considering an appeal. FreeEats.com ran into similar legal trouble in North Dakota in 2004. The firm contended that the state’s rules were pre-empted by federal law, but the North Dakota courts disagreed.

Earlier this month, the Supreme Court refused to take the case. Mr. Sandler said the fact that the unsolicited calls are irritating to some is not sufficient grounds to ban them. “It’s obnoxious, maybe, but nevertheless, so are a lot of things that are protected as free speech,” he said.