The bylaws decisions follow other Delaware court rulings that empower shareholders and increase corporate boards' accountability to them, said Andrew Hough, a business and finance partner at Atlanta's Powell Goldstein whose firm wasn't involved in the cases.

The stakes are high because the plaintiffs are investment and hedge funds who are trying to change the companies' management and direction, Hough said.

From a company's point of view, eleventh-hour changes to the ordinarily highly orchestrated annual meeting can disrupt the meeting and potentially the corporation and its current strategy, he said.

If dissident shareholders don't need to follow advance-notice requirements, they're "more likely to be successful in their proposals because it doesn't allow the corporation the time to conduct its own campaign against the proposals," Hough said.