WASHINGTON  More than 60 years ago, the Supreme Court ruled that the police were not entitled to enter a residence without a warrant merely because they smelled burning opium.

On Wednesday, at the argument of a case about what the police were entitled to do on smelling marijuana outside a Kentucky apartment, two justices voiced concerns that the court may be poised to eviscerate the older ruling.

“Aren’t we just simply saying they can just walk in whenever they smell marijuana, whenever they think there’s drugs on the other side?” Justice Sonia Sotomayor said, considering what a decision against the defendant would signal to the police. “Why do we even bother giving them a warrant?”

The old ruling, Johnson v. United States in 1948, involved the search of a hotel room in Seattle. The smell of drugs could provide probable cause for a warrant, Justice Robert H. Jackson wrote for the majority, but it did not entitle the police to enter without one.