Washington ? The Supreme Court on Thursday sharply curtailed prosecutors’ use of an anti-fraud law that was central in convicting politicians and corporate executives in many of the nation’s most prominent corruption cases. The ex-CEO of disgraced energy giant Enron and a Canadian media mogul, both in prison, are among the figures who could benefit from the ruling.

The justices voted 6-3 to keep the law in force, even as they joined unanimously in weakening it, and left it to a lower court to decide whether Jeffrey Skilling, the former Enron boss, and Conrad Black, the former newspaper owner, should have their convictions stemming from “honest services” fraud overturned.

The “honest services” law has been criticized by defense lawyers as the last resort of prosecutors in corruption cases that lack the evidence to prove that money is changing hands. It also has been called vague. But watchdogs consider it key to fighting white-collar and public fraud.

Melanie Sloan, executive director of Citizens for Responsibility and Ethics in Washington, said the decision “deprives prosecutors of an important tool in their efforts to fight public corruption. Previous convictions may be vacated and corrupt officials will have an easier time escaping accountability for their misdeeds.”