A Delaware court has rejected shareholder lawsuits opposing the acquisition of Plains Exploration & Production (UNKNOWN:PXP.DL2) by Freeport-McMoRan Copper & Gold (NYSE:FCX), and the Plains board is urging investors to approve the deal.

The companies announced the $6.9 billion acquisition proposal in December; PXP stockholders are entitled to receive per-share consideration consisting of 0.6531 shares of FCX common stock and $25 in cash.

A vote by Plains shareholders on approving the merger is scheduled for May 20 and after a chancery court in Delaware this week slapped down several shareholder lawsuits attempting to oppose the merger, Plains issued a press release to let investors know it still backs the union of the two companies.

It said the court found that the plaintiffs did not establish a reasonable probability of success on the merits of their claim that the PXP board of directors breached its fiduciary duties in connection with the proposed merger.

Plains says Freeport's bid is its "best and final offer," meaning there won't be any additional consideration offered, so shareholders have to decide the merits of proposal as it is, though management maintains it is in the best interests of its shareholders.

Headquartered in Houston, Plains has oil and gas properties in California, Texas, Louisiana, and the Gulf of Mexico.

McMoRan Exploration shareholders are set to vote June 3 on Freeport's proposed $3.4 billion acquisition of that company, announced at the same time as the Plains' deal.