TALLAHASSEE, Florida (Reuters) - A judge on Monday halted a new Florida law that requires low-income parents seeking federal cash assistance to pass a drug test before receiving any money.

In a 37-page ruling in Orlando, District Court Judge Mary Scriven granted an injunction barring the state from enforcing the new law until the case is resolved.

The American Civil Liberties Union of Florida sued on behalf of a University of Central Florida student who refused to take the drug test when he applied for Temporary Assistance to Needy Families, a federal program that provides cash assistance to families with children.

The ACLU argued that the drug tests are unconstitutional in other situations.

In her ruling, Scriven said the testing procedure could cause irreparable harm to recipients, who are required to pay for the tests and are barred from collecting benefits for at least six months if they fail.

The ACLU has a good chance of prevailing in its lawsuit, she said.

Plaintiff Luis Lebron, a single father and military veteran who plans to graduate in December with an accounting degree, was denied benefits when he refused to submit to a drug test, a requirement that Florida lawmakers approved earlier this year.

The law requires applicants for the funding to pay for and pass a urine test for illegal drugs, which costs between $25 and $45. Applicants who pass the test are reimbursed.

So far, the state says only 2 percent of applicants have tested positive for illegal drugs, a failure rate that is below that of the general population. A 2009 study by the U.S. Department of Health and Human Services found that 8.7 percent of Americans age 12 and older reported using illicit drugs.

The U.S. Supreme Court in a 1997 decision threw out a Georgia law requiring candidates for state office to certify they had passed a drug test. Since then, a federal court in Michigan threw out that state's attempt to require all welfare recipients to be tested.

"I'm delighted for our client and delighted to have confirmation that all of us remain protected from unreasonable, suspicionless government searches and seizures," said Maria Kayanan, the ACLU of Florida lead attorney in the case.

Florida Governor Rick Scott, who supports the requirement, was on a trade mission in Brazil on Monday and could not immediately be reached for comment. State attorneys arguing against the injunction said the searches were not illegal.

"No one forces an applicant to take the test. The plaintiff was notified of his right to refuse and has exercised that right," attorneys for the state wrote in legal arguments.

Scott previously signed an executive order requiring all state workers to undergo drug testing, but suspended the testing in June pending the resolution of a similar lawsuit that called the tests an illegal search of workers' bodies.

(Editing by Jane Sutton and Greg McCune)

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