A federal judge temporarily blocked police in Alexandria and Fairfax and Prince William counties yesterday from enforcing a new Virginia law barring the sale of drug paraphernalia.

District Judge Albert V. Bryan Jr. agreed with the Washington-based National Organization for the Reform of Marijuana Laws that enforcement of the law would do "significant, irreparable harm" to the 28 Northern Virginia business that challenged it yesterday in two lawsuits.

But Bryan rejected their request that his ban on the new law, scheduled to take effect on July 1, be made statewide. He said there was not enough time to notify all the state's prosecutors and police forces of such a step and restricted his order to the three jurisdictions named in the lawsuits.

The law, passed by the state legislature earlier this year with little controversy, is similiar to laws enacted by Maryland and 24 other states, according to the Drug Enforcement Administration. The Maryland law and most of the others have also been challenged in the courts, but according to area prosecutors, most of the challenges have been rejected.

Bryan's order banning enforcement of the Virginia law will remain in effect until a July 15 hearing on the case.

The Virginia statute prohibits the sale of materials to be used "for the cultivation, preparation or use" of illicit drugs, including marijuana. A second section of the law states that the sale of items not obviously drug-related, such as cigarette rolling paper and pipes, may be illegal if the store offering them also carries literature dealing with drug use, or if police can prove intent to sell for drug use.

The marijuana group, called NORML, charged in one of the suits that such laws have had a "a chilling effect" on free speech rights of individuals to distribute T-shirts, novelty items and literature on marijuana use, and that the statute is too vague to be constitutional.

Attorneys for the 20-store Virginia Tobacco Accessories Trade Association. RPM Associates and the Tobacco Accessories Distributing Co., which filed the second suit, said the statute that will force them to close their businesses and suffer "severe economic losses."

In court yesterday Prince William County prosecutor Paul Ebert, Alexandria assistant prosecutor Drew Carroll, and Deputy Virginia Attorney General James E. Kulp contended that the lawsuits had been filed too suddenly for them to prepare a cogent defense.

"The plaintiffs come to court with unclean hands," said Assistant Fairfax County Attorney Benjamin Bull. "This 'emergency' situation has been orchestrated by the plaintiffs."

Kulp said he drove from Richmond yesterday morning and did not see the lawsuits until 15 minutes before the hearing began. Carroll said he was given the asignment Monday evening just as his law library was closing.

Johathan Shapiro, attorney for the Northern Virginia businesses, argued that "the law is so vague that it allows the cop on the street to make his own decision" on what is or is not drug paraphernalia in a given situation.

Attorney JOHN K. Zwerling also argued that there is no clear assessment of what is -- or is not -- drug paraphernalia and that certain businesses might be singled out when other, more "established stores might receive no scrutiny at all.

Prosecutor Ebert agreed later in an interview that there may be serious problems in enforcing the statute. "It's going to be difficult to prove the purpose of the sale. We have to show criminal intent on the part of the seller," he said.

"It's the same old thing of owning a firearm. It's not illegal to have one, but it's illegal to have one for use in a crime."