Although dual-class share structures are controversial and have long been opposed by shareholder-rights advocates, they have been growing in popularity, especially in Silicon Valley. Entrepreneurial founders are often reluctant to cede control; Facebook, Google’s parent company Alphabet and Snap are all dual-class share companies. But so are Berkshire Hathaway, Ford Motor, Comcast and The New York Times Company.

Should CBS ultimately prevail in what would be a highly unusual attempt to dilute a controlling shareholder, a bevy of dual-class companies will no doubt be scrambling to rewrite their bylaws.

The conflict is magnified in this instance because Ms. Redstone is the controlling shareholder in both parties to the proposed merger.

“I don’t think there’s any question that the Redstones have a clear conflict of interest in this situation,” said Margaret Blair, a professor and expert in corporate governance at Vanderbilt University School of Law. “The law is very clear that the authority for running the corporation lies with the board. If the board feels the controlling shareholder is interfering with the best interest of the other shareholders, courts will defer to the board, and I think they should.”

(At a hearing on Wednesday, a judge in Delaware granted CBS’s request for the temporary restraining order. The judge is expected to issue a more expansive ruling on Thursday concerning whether the result of the CBS board’s planned vote will be allowed to go into effect.)

Such cases are rare, because directors who dare to defy a controlling shareholder’s wishes, as the CBS directors have done, can simply be replaced. There was widespread amazement on Wall Street this week that Ms. Redstone hadn’t sensed the rebellion coming, and moved to replace the CBS directors or curtail their powers. Now her hands are tied, at least temporarily.