The state of Iowa on Tuesday asked the Supreme Court to uphold a state law that gives the police essentially blanket authority to search a car after issuing the driver a citation for speeding or another routine traffic violation.

The Iowa Supreme Court upheld the law, the only one of its kind, by a 5-4 vote last year. But the justices responded to the state's arguments with considerable wariness. Justices across the ideological spectrum worried aloud that an expansion of the current rule, under which the police may conduct a search as an aspect of taking a person into custody in a formal arrest, would give the police too much power.The case is an appeal by a man who was stopped for driving 43 mph in a 25 mph zone. The police officer gave him a speeding ticket after determining that his license was valid and that there were no outstanding warrants for his arrest. Then the officer searched the car, finding a small quantity of marijuana and a pipe, and arrested him.

Twenty-five years ago, the Supreme Court validated a practice known as "search incident to arrest," which is an exception to the ordinary Fourth Amendment requirement that a search be supported by probable cause or at least some level of suspicion of a crime.

Once there was probable cause to make an arrest, the court said then in United States vs. Robinson, a search of the person arrested, as well as the area under his control, would be deemed reasonable, without further need to establish probable cause to search. It made sense, the court said in the 1973 case, to authorize such a search to preserve evidence and to protect the arresting officer's safety.

In the argument on Tuesday, several justices, including the court's more conservative members, suggested that the rationale of the "search incident to arrest" doctrine did not apply in the context of a simple speeding ticket.

With a speeding violation, "the offense is complete when the car is brought to a stop," Chief Justice William H. Rehnquist said, adding, "There is no more evidence to look for."