After turning down a 62 percent premium for shareholders in the form of Microsoft’s takeover bid, Yahoo opened itself to litigation from unhappy stakeholders.

Unhappiness manifested itself quickly as one group decided they would rather take their chances with Microsoft acquiring Yahoo, and filed a lawsuit to force Yahoo to consider takeover overtures.

A Bloomberg report said the Wayne County Employees’ Retirement System of Michigan, owner of about 13,600 Yahoo shares, sued Yahoo in Delaware’s Court of Chancery. Theirs could be the first of several others, depending on how Yahoo handles the ongoing negotiations.

Yahoo wants no part of a Microsoft buy, and announced they consider Microsoft’s initial $44.6 billion bid as undervaluing the company. If they choose to use it, Yahoo has a ‘poison pill’ defense they could invoke to keep out of Microsoft’s hands.

But the report said use of the poison pill appears unlikely, as it would further anger shareholders who have seen Yahoo lose more than half its market value over the past two years. Hedge fund president Nancy Havens of Havens Advisors told Bloomberg that Yahoo is “between a rock and a hard place” now, with only a goal of getting a sweetened price out of Microsoft.

Microsoft responded to Yahoo’s rejection of its offer with the intent of pressing its acquisition. Top Microsoft executives like CEO Steve Ballmer will work on convincing big institutional investors that the deal makes sense for both Microsoft and Yahoo.