Two Mexican brothers arrested in the largest heroin seizure in California history walked free this week after federal prosecutors in San Diego dropped the charges against them. Prosecutors had little choice because a federal judge ruled last month that police had violated the Fourth Amendment's ban on warrantless searches and threw out the evidence against them. Two others arrested in the case have already pleaded guilty and are awaiting sentencing.

At the time of the Valentine's Day bust, Immigration and Customs Enforcement (ICE) nearly dislocated their shoulders patting themselves on the back for uncovering what they described as a major heroin, methamphetamine, and marijuana trafficking operation. But their eagerness to search and make arrests eventually cost them the case.

It all started when ICE agents at the San Ysidro border crossing found a car with nearly 12 kilos of Mexican heroin hidden inside. The driver was allowed to continue to his destination in Anaheim under ICE surveillance. The driver met with another man, then drove to an Anaheim house and pulled into the garage. Without waiting for a search warrant, ICE agents entered and searched the house, arresting six people and seizing 121 pounds of heroin, 34 pounds of marijuana, and 3 pounds of methamphetamine, along with about $3,500 in cash.

Attorneys for the two Mexicans argued in court papers the men had been staying at the Anaheim home and had a "reasonable expectation to privacy" guaranteed by the Fourth Amendment. They also argued that there was no threat to officer safety or that the evidence would be destroyed if ICE waited to get a search warrant.

Federal prosecutors argued that agents had no time to obtain a search warrant and that the drugs and the driver who led agents to the house were at risk, but US District Court Judge James Selna wasn't buying it. He instead ruled for the defense, holding that the search was unconstitutional and that the evidence derived from that search -- the seized drugs -- could not be admitted in court.

"To me, the issue is a rule of law and it won," said attorney Joel Levine, who represented one of the brothers.