An SEC regulation requiring publicly-traded companies to offer all new issues of a security to all current shareholders of the same class. For example, if a company issues more Class A shares, it must allow all current Class A shareholders to participate in the offering. Likewise, if it wishes to buy back all class A shares, it must allow all shareholders to sell their shares back to the company.
An SEC rule that prohibits bidders and target companies from excluding a stockholder or a group of stockholders from a tender offer. See also exclusionary tender offer.