Washington ? The Supreme Court, led by Chief Justice John Roberts, gave a skeptical hearing Tuesday to the government’s contention that it has broad powers to block development on private wetlands that are far from rivers or bays.

The Clean Water Act gives federal authorities the power to protect the “navigable waters of the United States,” but the court is reconsidering whether that power extends well inland to wetlands and small streams.

Roberts and Justice Antonin Scalia sharply questioned U.S. Solicitor Gen. Paul Clement, who defended the broad reach of the law. Both said they thought there must be a limit to federal authority.

Scalia said it was “absurd” and “extravagant” to claim that ditches and storm drains are part of the navigable waters of the United States.

There must be a point where the law “says ‘stop,'” Roberts said. Otherwise, “every drop of water” on any field or farm in America is subject to federal jurisdiction, he said.

In the past, Justices Anthony M. Kennedy and Clarence Thomas have voted to limit the federal authority over wetlands. If new Justice Samuel Alito joins them, a five-member majority could sharply limit the federal law that has been credited with cleaning up the nation’s rivers and lakes.

Alito made only a few comments during the argument, and did not tip his hand as to how he will rule.

All the justices sounded concerned about toxins and pollutants being put directly into a tributary, such as a flowing stream.

Rivers and lakes can be protected only if pollution is stopped at its source, said Justice David Souter. If the federal protection does not move upstream, “all you have to do is dump the pollutants far enough upstream and you get away scot free,” he said. “It’s hard to believe Congress intended that.”

When the argument ended, the justices sounded closely split, with Roberts and Scalia searching for a way to exclude inland wetlands on the theory that filling them in would not have a direct impact on a river or bay.

A decision in the case, Rapanos vs. United State, can be expected in several months.