NEW YORK—A New York state judge has handed Alliant Insurance Services Inc. a victory in ongoing litigation with Aon Corp. over allegations that Alliant poached Aon employees.

In an order filed earlier this month, New York State Supreme Court Judge Bernard J. Fried rejected Aon's bid to have Newport Beach, Calif.-based Alliant held in contempt for allegedly violating a preliminary injunction the judge issued last year.

Chicago-based Aon alleged that the former executives conspired with Alliant to solicit at least 40 other employees of Aon's construction services group to quit Aon and join Alliant in 2011.

In the December ruling, Judge Fried temporarily barred Alliant and some former Aon employees who had joined Alliant's construction services group from soliciting business from certain Aon clients—those on whose accounts the former Aon employees had worked or served as producers.

In his order, Judge Fried said Aon was “likely to succeed on the merits” of several of its claims against its former employees and Alliant. The allegations against the former employees include breach of contract and violations of fiduciary duty, while those against Alliant include allegations that it had interfered with employment contracts.

Aon had alleged that Alliant violated the order because of materials sent this year to certain Aon clients, arguing that it should be held in contempt. However, Judge Fried rejected that argument, holding that Aon failed to establish “clear and convincing evidence” that Alliant had indeed disobeyed the order.

“We are pleased that the court has rejected Aon's efforts to improperly expand the injunction beyond what Justice Fried previously ruled,” Jeffrey S. Klein, lead counsel for Alliant and chair of the employment litigation practice at Weil, Gotshal & Manges L.L.P., said in a statement. “This is an important and positive development, and we will continue to defend our client against Aon.”

“The parties are continuing to pursue their respective rights and we look forward to pursuing a favorable outcome for Aon,” an Aon spokesman said in an email.