IAC/InterActiveCorp. Chairman Barry Diller won a big victory in his bitter legal dispute with Liberty Media Corp. Chairman John Malone, as a Delaware court ruled Mr. Diller can proceed with efforts to spin off four of IAC's largest units into multiple companies.

The ruling is the latest in a high-profile legal showdown between billionaire moguls Diller and Malone, who has a controlling interest in IAC/InterActive.

A 1995 proxy agreement between Diller and Malone, Malone gave Diller the right to exercise Malone's 60 percent voting authority.

To fully grasp the unusual character of this dispute requires an understanding of two basic facts that rule the governance of IAC, wrote the judge, Vice Chancellor Stephen P. Lamb, in his opinion, which was released Friday.

The ruling came two weeks after a five-day trial in which Mr. Malone, the billionaire chairman of Liberty Media, and who is the majority voting stockholder in IAC, had sought to gain control of IAC. With the court decision, Mr. Diller can now go ahead with his plan to break IAC into five companies: the HSN home shopping network; Ticketmaster; Interval, a vacation time-share company; and LendingTree, a mortgage broker, as well as IAC, which would include Match.com and Ask.com.

The ruling, however, left the door open for Mr. Malone to challenge the breakup plan after it is approved by IAC's board. The two sides also could negotiate a deal in which Liberty would give up its IAC stake in exchange for IAC assets. IAC shares were up about 6 percent in after-hours trading.

I wish this hadn't happened, but it did, Mr. Diller said in an e-mail statement. Now it's over and we can all get on with our work and lives.