A federal judge has barred Utah from enforcing a new sex-offender law against a Weber County man whose lawsuit against the state could be a test case that decides whether the law is constitutional.

House Bill 43, which is to go into effect today, requires registered sex offenders to hand over to the Department of Corrections all passwords to online social networking sites, such as MySpace and Facebook.

During a hearing Monday, U.S. District Judge Tena Campbell found that the enforcement of the law against "John Doe" would cause him "irreparable harm" before the court had a chance to review the constitutionality of the state law.

The decision deals a small legal blow to the state. At one point, however, Campbell considered enjoining the state from enforcing the new law altogether instead of just applying her ruling to one sex offender.

The man, who court documents only identify as "John Doe," claims the new law violates his Fourth Amendment right against unlawful search and seizure.

According to a federal suit filed last week, Doe says he was found guilty of carnal knowledge and sodomy on a minor in a military court in 2005 and sentenced to 18 months confinement. In addition to a bad conduct discharge from the Air Force, Doe served 13 months in the military corrections system and was released early for good behavior.

Doe says he has never been under the jurisdiction of the Utah Department of Corrections, which manages Utah's sex-offender registry, but was forced to register as a lifelong sex offender. Specifically, Doe claims the new provision unconstitutionally requires registered offenders to hand over online identifiers and passwords to social networking and blogging sites. He argues that although the state claims the purpose is to "monitor" offenders, the state can also gain access to sites and plant evidence against people.

In court, assistant Utah attorney general Sharel Reber said the information gathered will be kept in a database by the state and will not be made public, but rather used for law enforcement purposes only. Reber said the new law will not violate the Fourth Amendment because law enforcement requesting access to the database must first seek a warrant from a judge. The state already gathers other personal information from offenders, such as home addresses and Social Security numbers.

Campbell said the suit presented "thorny and complex issues," which needed to be fully studied. Because she saw the enforcement of the law against Doe as doing potential "irreparable harm," Campbell ordered that Doe be registered as a sex offender under the old law for now.