Don Margotta, a finance professor who has written extensively about hostile takeovers at Northeastern University in Boston, said that staggered board structure “is very effective in fighting off takeovers, or at least slowing them down.”

On top of that, Margotta said, are Ohio laws that prevent investors from buying more than 20 percent of a company without permission from other shareholders. That law could stop Schulman from getting enough votes to win seats on Ferro’s board.

Still, with an offer on the table and shareholders howling for change, Margotta and Johnson said the board will be under pressure.