In the case of Bell Atlantic Corporation v. William Twombly, the U.S. Supreme Court ruled in favor of Bell Atlantic (now Verizon Communications). The plaintiffs, a group led by William Twombly, had filed an antitrust lawsuit against major telecommunication providers alleging that they conspired to inflate prices and reduce competition in violation of Section 1 of the Sherman Act. However, their complaint was dismissed for failing to provide enough factual evidence to support their claim beyond mere speculation or conjecture. On appeal, the Supreme Court upheld this decision stating that it is not sufficient for a complaint under federal rules just to suggest plausible grounds for relief but must contain more than labels and conclusions or formulaic recitation of elements; rather it should show entitlement with detailed facts supporting each claim.

In the dissenting opinion for Bell Atlantic Corporation v. Twombly, Justice Stevens argued that the majority's decision to dismiss the case at such an early stage was premature and inconsistent with precedent. He contended that it is not necessary for a complaint to include detailed factual allegations in order to survive a motion to dismiss; rather, it only needs to provide fair notice of what the claim is and its grounds. The plaintiffs' allegation of parallel conduct among telecommunication companies sufficed as circumstantial evidence of conspiracy under antitrust laws, according to Stevens. Furthermore, he criticized the majority's reliance on economic theory over legal principles in their reasoning process - stating that courts should be cautious about using theoretical models as definitive proof of legality or illegality. Lastly, he expressed concern about how this ruling could potentially raise barriers for future plaintiffs seeking redress through class action lawsuits by requiring them to present more extensive evidentiary support at an earlier stage.