CHICAGO (

TheStreet

) -- The

Chicago Board Options Exchange

will have to resolve legal challenges to its ownership structure before being sold, according to a published report.

CME Group

(CME) - Get Report

, the world's largest futures market, has hinted about buying CBOE,

Crain's Chicago

reported over the weekend. But a purchase largely depends on CME's Chicago Board of Trade resolving a lawsuit over CBOE's ownership claims, analysts told

Bloomberg

. The contest for CBOE may last into the second half of 2010 as the biggest market for U.S. equity derivatives resolves the lawsuit over who owns it.

A group of former CBOT members sued the CBOE in 2006, claiming the group is entitled to swap CBOE trading rights that date to 1973 into shares of the options exchange. The CBOE claimed CBOT's sale in 2007 eliminated the members' ownership claims, according to

Bloomberg

.

A CBOE spokeswoman said there was no formal bid yet and that negotiations were on hold until Wednesday, which is the deadline for filing appeals in the lawsuit. Last month, CBOE Chairman Bill Brodsky said the firm expects to demutualize, or exchange stock for its members' ownership interests, by the end of the first quarter after settling the CME lawsuit,

Bloomberg

reports.

Citing Chicago-based Options Clearing Corp.,

Bloomberg

reports CBOE handled 31.4% of the equity and index option orders on all seven U.S. exchanges as of last month. CME, meanwhile, has had a strong hold on futures with the purchase of CBOT and the New York Mercantile Exchange.

Crain's

said an acquisition would value CBOE at as much as $5 billion, valuing each CBOE seat at about $4 million, a 50% premium.