Dissidents such as Politan are now required to reveal other Masimo investors they have spoken with and who support their push for change. They must also disclose any other companies in which they have nominated directors in the past 36 months, as well as plan to do so, in the coming year.

“Is this a thinly veiled attempt to stop activism?” asked Michael Klaunser, a Stanford Law School professor. “No. It’s not veiled at all; it’s utterly clear.”

Klaunser called such rules counterproductive.

“A lot of activism is done on a confidential basis, resulting in compromise, and resulting in pro-shareholder changes in strategy and tactics,” he said. “A strength for an activist could be getting these things done without public disclosure.”