People lined up in the fog at the the U.S. Supreme Court Tuesday to hear cases before the court. (J. Scott Applewhite/AP)

As the Supreme Court once again delved into the meaning of the Constitution’s prohibition against unreasonable searches and seizures by government officials, Justice Stephen G. Breyer was characteristically optimistic.

“I’m looking for something simple,” he told one of the lawyers in the case Tuesday.

But two hours of oral arguments in two cases that each touched on the Fourth Amendment showed that the simply worded constitutional declaration defied simple interpretation.

One case involved the unauthorized driver of a rental car and whether he had a right to prohibit police from searching the trunk of the car without his consent. The other involved an officer’s decision to enter a suspect’s carport without a warrant because he believed he’d find a stolen motorcycle hidden under a tarp.

Lawyers for the men arrested in both of those cases presented their objections to the justices in dire terms.

“In this case, the government seeks to transform a violation of a car rental agreement into a rule where unlisted drivers have no ability to even invoke the Fourth Amendment,” said Washington lawyer Robert M. Loeb, who was representing Terrence Byrd, convicted of having heroin and body armor in the trunk of a Ford Fusion rented from Budget.

In the second case, all acknowledged that the search of a house or the area immediately adjacent to it usually requires a warrant. But Richmond lawyer Matthew A. Fitzgerald said Virginia state officials contend police don’t need one to “search a vehicle anywhere that he finds it and [that he] may go anywhere that he needs to in order to access that vehicle.”

Justices were troubled by both cases, in part because it seemed difficult to come up with tests and rules that would apply beyond the parties in question.

“One of the things that I think is very important in these types of cases is the ability to give clear guidance not only to the courts but to the police,” Chief Justice John G. Roberts Jr. said in the rental car case.

Byrd was driving a car rented by his fiancee and longtime companion, with whom he shared five children. A Pennsylvania state trooper followed the car for a bit and pulled Byrd over for a minor traffic violation. He said he thought Byrd was acting suspiciously and discovered Byrd was not listed on the rental agreement.

The officer asked Byrd if he could search the vehicle, but also said he did not need permission because Byrd was not the authorized driver. Byrd eventually filed a conditional plea of guilty to the drug and body armor charges, reserving the right to contest the legality of the search.

Because the authorized renter of the car gave him permission to place his property in the locked trunk of the car, Loeb told the court, Byrd had a reasonable expectation of privacy.

Justice Sonia Sotomayor appeared to be the justice most on Byrd’s side.

“If we rule that someone without permission . . . has no expectation of privacy even when the renter has given it to them, then what we’re authorizing is the police to stop every rental car and search every rental car, without probable cause, that might be on the road,” she said.

But Justice Department lawyer Eric J. Feigin said Byrd’s rights were limited. “The key distinction here is that he’s claiming a personal Fourth Amendment right,” Feigin said. “As an unauthorized driver, he doesn’t have any connection to the car at all.”

But Roberts pointed out he did have the permission of his fiancee. And the justices came up with more examples. What about a dad who gave his son permission to drive the car, but the son let a friend drive it? Could even an authorized driver of a rental deny police permission to search the car if the car rental company made agreement to such searches part of the rental contract?

In the second case, the justices had to decide whether the motorcycle’s proximity to the house required more stringent rules than if police had observed it elsewhere, such as on the street.

“What is the additional invasion of privacy?” asked Justice Samuel A. Alito Jr. “The invasion of privacy that’s involved in walking a few feet up the driveway?”

But Justice Elena Kagan offered a different view. The court in the past has recognized the home as the “most sacrosanct of places. And, actually, we don’t think that the home stops at the door; we think that there are some areas like the porch and like the driveway or whatever, and we can argue about exactly what those areas are, but there are some areas which are just as sacrosanct as your living room.”

The cases are Byrd v. United States and Collins v. Virginia.