The controversy surrounding a Berkshire Hathaway executive's stock trading before an acquisition by the firm shines a light on what some say could be a gap in securities disclosure: There is no rule requiring that executives' holdings in an acquisition target be revealed.

Generally, it is up to a public company to decide whether executives' holdings of public securities rise to the level of "material" information that should be disclosed. The test, lawyers say, is whether a reasonable investor would consider the information important in making a decision to buy, sell or hold the shares. In a deal situation, conflicts of interest rules can come into play but won't necessarily result in a disclosure decision, they say.