The police practice of ‘‘wiring’’ informants and recording suspects’ conversations in their homes and in vehicles without a warrant is a violation of privacy rights, the Montana Supreme Court has ruled.

In a split decision Wednesday, the high court said a district judge in Gallatin County should have suppressed evidence against two men that was gathered by confidential informants armed with hidden microphones who entered the men’s homes without warrants in 2004.

The ruling was hailed by defense attorneys, but decried by a prosecutor as a major setback for law enforcement.

In one case before the high court, Michael T. Goetz pleaded guilty to selling one gram of methamphetamine to an informant, who wore a body wire into Goetz’s home. In the other, Joseph P. Hamper pleaded guilty to drug charges after the Missouri River Drug Task Force recorded him twice selling $50 worth of marijuana to an informant, once in the informant’s car and once in Hamper’s home.

‘‘The electronic monitoring and recording of those conversations without a warrant or the existence of an established exception to the warrant requirement violated the Defendants’ rights’’ under the Montana Constitution, according to the decision, which was written by Chief Justice Karla Gray. Justices Jim Rice and John Warner dissented.

The attorneys for Goetz and Hamper praised the decision.

‘‘It’s a great victory for the constitution and the people of Montana,’’ said Bozeman attorney Brian Gallik, who represented Goetz.

The ruling means officers will have to have probable cause before they can use wires and ‘‘can’t go on fishing expeditions,’’ said public defender Peter Ohman, who represented Hamper.

Ohman said the ruling reinforces a provision in the state constitution that says Montanans’ right to privacy ‘‘shall not be infringed without the showing of a compelling state interest.’’

‘‘Some people will try to make it look like a ruling that protects drug dealers, but it’s really not,’’ he said. ‘‘It recognizes that all of us have a right to privacy.’’

Deputy Gallatin County Attorney Todd Whipple, who helped prosecute the case, called Wednesday’s decision a ‘‘huge blow to law enforcement.’’

‘‘It essentially handcuffs the officers and takes the handcuffs off the criminals,’’ Whipple said.

Warrantless electronic monitoring and recording of conversations with confidential informants has been a ‘‘standard law enforcement technique’’ for 20 years, he said. The practice has been upheld in previous rulings by the state Supreme Court, so Wednesday’s ruling marks a change in direction, Whipple said.

In his dissent, Rice said he disagreed that the case was about the privacy of Montanans in their homes, or about one-on-one conversations conducted in private settings.

‘‘Rather, this case is about avoiding the truth — the defendants’ raising of a privacy claim to keep the truth, that is, the recording of their own words, from the jury and thereby gaining a tactical advantage by escaping the strong evidence of their crimes,’’ Rice wrote.

The defendants in this case were aware of the police involvement but continued to sell drugs, he said.

‘‘Their actions were not consistent with the desire for privacy,’’ Rice wrote. ‘‘Indeed, I believe it is untenable for the Court to conclude that society would find reasonable the privacy claims against the consensual monitoring of such actions. The District Court rightly concluded that society would not find this connived claim reasonable.’’

Ohman, the public defender, said Wednesday’s ruling means evidence against Goetz and Hamper that was collected with the recording devices will be thrown out, and the cases will be remanded to District Court. However, the defense attorneys said it’s possible that both Hamper and Goetz have already completed their deferred sentences.

The high court’s decision wasn’t applied retroactively, so previous cases likely will not be affected, Whipple said.