Executives and board members probably haven't worried much about their 10b5-1 stock trading plans. That's about to change.

In recent months, renewed media and shareholder attention has led to growing scrutiny of the plans, which allow insiders to sell shares on preset days or intervals to avoid accusations of insider trading. The Council of Institutional Investors, an association of pension funds and other large shareholders representing combined assets of $3 trillion, has recently expressed concerns about potential misuse of the plans and urged the Securities and Exchange Commission to consider new rules.

In a letter to the SEC, Jeff Mahoney, CII's general ...