For purposes of this opinion the Court assumed there would be an enforceable agreement under Massachusetts state law. Its decision to not enforce the arbitration policy turned on a requirement in the ADA first articulate in its 1999 decision in Rosenberg v. Merrill Lynch. Under the Rosenberg standard, the Court found its task here to be:
whether General Dynamics's e-mail announcement of the Policy provided sufficient notice to the plaintiff that his continued employment would constitute a waiver of his right to litigate any employment-related ADA claim, thereby rendering judicial enforcement of that waiver appropriate.
To be blunt, the e-mail announcement undersold the significance of the Policy and omitted the critical fact that it contained a mandatory arbitration agreement. The result was that a reasonable employee could read the e-mail announcement and conclude that the Policy presented an optional alternative to litigation rather than a mandatory replacement for it. Because that primary communication lends itself to such a conclusion -- rather than cluing in the reader by including a simple statement of the kind contained in the Policy itself that '[t]he mutual obligations set forth in [the] Policy shall constitute a contract between the Employee and the Company' -- we conclude that it failed to put the recipient on inquiry notice of the unilateral contract offer contained in the linked materials.
Just as an aside, although you were not yet quite sure why, you had some idea how the case might turn out just by the Court's choice of language in describing the plaintiff's relationship to the employer: "For a period of nearly three years, plaintiff-appellee Roderick Campbell toiled as an at-will employee of General Dynamics Government Systems Corporation." Employees a court views as 'toiling' are often on their way to judicial success.