ORLANDO, Fla. - A federal judge temporarily blocked Florida's new law that requires welfare applicants to pass a drug test before receiving benefits on Monday, saying it may violate the Constitution's ban on unreasonable searches and seizures.

Judge Mary Scriven ruled in response to a lawsuit filed on behalf of a 35-year-old Navy veteran and single father who sought the benefits while finishing his college degree, but refused to take the test. The judge said there was a good chance plaintiff Luis Lebron would succeed in his challenge to the law based on the Fourth Amendment, which protects individuals from being unfairly searched.

The drug test can reveal a host of private medical facts about the individual, Scriven wrote, adding that she found it "troubling" that the drug tests are not kept confidential like medical records. The results can also be shared with law enforcement officers and a drug abuse hotline.

"This potential interception of positive drug tests by law enforcement implicates a 'far more substantial' invasion of privacy than in ordinary civil drug testing cases," said Scriven, who was appointed by President George W. Bush.

The judge also said Florida didn't show that the drug testing program meets criteria for exceptions to the Fourth Amendment.

The injunction will stay in place until the judge can hold a full hearing on the matter. She didn't say when that hearing will be scheduled.

More than two-dozen states have also proposed drug-testing recipients of welfare or other government assistance, but Florida was the first state to enact such a law in more than a decade. Should any of those states pass a law and face a court challenge, Scriven's ultimate ruling would likely serve as a legal precedent.

The law's proponents include Gov. Rick Scott, who said during his campaign the measure would save $77 million. It's unclear how he arrived at those figures. A spokesman for the Florida Department of Children and Families deferred all comments to the governor's office.

"Drug testing welfare recipients is just a common-sense way to ensure that welfare dollars are used to help children and get parents back to work," said Jackie Schutz, a spokeswoman for Scott. "The governor obviously disagrees with the decision and he will evaluate his options regarding when to appeal."

Earlier this year, Scott also ordered drug testing of new state workers and spot checks of existing state employees under him. But testing was suspended after the American Civil Liberties Union also challenged that policy in a separate lawsuit.

Nearly 1,600 applicants have refused to take the test since testing began in mid-July, but they aren't required to say why. Thirty-two applicants failed the test and more than 7,000 have passed, according to the Department of Children and Families. The majority of positives were for marijuana.

State officials said Monday that applicants previously denied benefits for testing positive or refusing the test could reapply immediately. The Department of Children and Families will also approve all pending applications that await drug test results.

Supporters had argued applicants skipped the test because they knew they would have tested positive for drugs. Applicants must pay $25 to $35 for the test and are reimbursed by the state if they pass. It's unclear if the state has saved money.

Under the Temporary Assistance For Needy Families program, the state gives $180 a month for one person or $364 for a family of four.

Those who test positive for drugs are ineligible for the cash assistance for one year, though passing a drug course can cut that period in half. If they fail a second time, they are ineligible for three years.

Lebron, who is the sole caretaker of his 4-year-old son, said he's "happy that the judge stood up for me and my rights and said the state can't act without a reason or suspicion."

The ACLU says Florida was the first to enact such a law since Michigan tried more than a decade ago. Michigan's random drug testing program for welfare recipients lasted five weeks in 1999 before it was halted by a judge, kicking off a four-year legal battle that ended with an appeals court ruling it unconstitutional.

Kennedy reported from Miami.