The legal challenge comes from an unspecified number of American shareholders.

Most American shareholders sold their stakes soon after the companies were combined.

As a result, foreign investors are no less spooked than they were in the 1890's, and American shareholders have flipped from euphoria to gloom.

The disclaimers have not been tested in court, and it is not clear how they affect American shareholders.

As long as the primary trading market for a stock is overseas, American shareholders can be ignored.

B.P. has said it would like to increase American shareholders' interest in the company to 15 percent, from 6 percent.

Moreover, American shareholders often cast their votes by mail or the Internet.

Companies whose securities now trade in the United States generally cannot leave unless the number of American shareholders falls below 300.

Often American shareholders do not want to hold foreign shares or, in the case of some pension funds, would be prohibited from doing so.

"This is a great day for the American shareholder."