NEW YORK—The New York state attorney general has decided not to pursue further action against two former Marsh Inc. executives whose convictions on violations of New York antitrust law were dismissed.

The attorney general could have sought to retry the case, although last month it dropped its appeal of a July 2 decision by New York County Supreme Court Judge James A. Yates that tossed out the convictions of former Marsh Managing Directors William Gilman and Edward J. McNenney.

In the opinion, the judge cited new evidence that “undermines the court’s confidence in the verdict,” including documents that weren’t disclosed at the time of the trial that would have proved “invaluable” to the defense as well as contradictory statements by witnesses who cooperated with the prosecution.

The attorney general’s office decided not to retry the case last week, according to a statement by Palo Alto, Calif.-based Cooley L.L.P., the law firm that represented Mr. McNenney.

Although the attorney general’s office already had dropped its appeal, the office “had not said that it would not retry the case,” a spokeswoman for Cooley said in an e-mail Friday. “If the (attorney general) had won the appeal it withdrew, the conviction would have stood; and if the AG had lost that appeal, the AG still could have tried the case again. Withdrawing the appeal did not mean that the AG could not retry the case,” the spokeswoman said.

Messrs. Gilman and McNenney, the first former Marsh executives to face trial in the case, were accused of colluding with employees at various insurers to rig the market for excess casualty insurance between 1998 and 2004. Judge Yates convicted the men in February 2008 of violating New York antitrust law, but acquitted them of 20 counts of fraud and larceny in connection with the alleged bid-rigging.

The New York attorney general’s move ends a series of failures by prosecutors targeting individual brokers named in 2004 during then-New York Attorney General Eliot Spitzer’s investigations of alleged bid-rigging and other practices by brokers and insurers.