US Bank regulators may roll back part of regulations put in place to implement the Volcker rule.

The US Comptroller of the Currency asked for comments on August 7 about how the Volcker rule is working, with particular emphasis on what banks and activities should be caught in its net. Comments are due by September 21.

The Volcker rule, named after former Federal Reserve Board Chairman Paul Volcker, is supposed to keep banks out of risky investments that might cause a bank to collapse and draw on federal insurance for bank deposits. Volcker wrote out his original idea in a page and a half. The implementing regulations (including the preamble explaining them) are more than 900 pages.

The Volcker rule was enacted in July 2010. It prevents banks with federally-insured deposits and their affiliates from engaging in “proprietary trading” — defined as trading in securities for the bank’s own account to benefit from short-term price movements — and from investing in any “covered fund” — which the bank regulators have defined as a subset of entities that would be considered “investment companies” by the US Securities and Exchange Commission. While it is not always clear whether an entity is an “investment company,” a company that is engaged directly in an active business or as a holding company whose sole assets are shares or other ownership interests in an active business company is generally not an investment company.

The Comptroller listed a number of complaints that banks have about the Volcker rule. They include that the implementing regulations are “overly complex and vague,” banks “sometimes are not able to distinguish permissible from prohibited activities” despite their best efforts to do so, and the net has been cast so broadly that banks have been forced to curtail market-making, hedging and asset liability management that is economically useful. (For a discussion about the how the Volcker rule affects bank participation in tax equity transactions, see “The Volcker Rule” in the February 2014 NewsWire.)