The Hyogo Prefectural Assembly on Monday passed an ordinance aimed at regulating sellers of law-dodging "dappo" (loophole) narcotics.

The drugs have a chemical formula that differs slightly from that forbidden by law. They have been blamed in a series of traffic collisions in which the driver reportedly took the products, which the government has officially described as "dangerous drugs."

The Hyogo assembly approved the measure unanimously. The ordinance is scheduled to come into force Dec. 1 as Japan's first local law aimed at regulating sellers of such drugs.

Under the ordinance, the governor will designate approved sellers of such drugs. The measure defines these drugs as those that can have a poisonous effect on users even if not banned by law.

The products, which often carry euphemisms such as aromatics, incense or herbs, will be required to bear the names and addresses of the sellers and producers. The ordinance also requires that sellers explain the potential dangers to buyers.

The prefectural government will have the power to order that the drugs are suspended from sale.

In June, a 37-year-old man reportedly under the influence of a dappo drug drove a car into pedestrians in the Ikebukuro district in Tokyo, killing a Chinese woman and injuring seven other people.