The FDIC recently clarified how bankers can invest in trust preferred securities by saying that state nonmember banks are not limited in the same way national banks are, a ruling bolstering the state charter.

National banks, which are overseen by the Office of the Comptroller of the Currency, have a limit of 10% per issuer. The FDIC said that limit does not apply to state non-member banks. The only limit is the one imposed by each state.

"I think what the FDIC’s letter does is clarify the state banks’ flexibility in their capitalization, and that can only be a good thing," said Ellen Lamb, spokeswoman for the Conference of State Bank Supervisors.

The OCC, for its part, said the issue is one of many it is monitoring in its ongoing efforts to be sure the national banking charter is competitive. The 10% limit is mandated by law, a spokesman said, and would have to be changed by Congress. Although the agency would be willing to ask Congress for an increase if it seemed important to its banks, the spokesman said, the agency would also have to consider safety and soundness issues.