Paul Volcker was federal reserve chairman from 1979 to 1987 under both Presidents Carter and Reagan and was credited with single heavy handedly squashing the stagflation of the 1970's and lowered inflation from over 13% to 3% in just under 2 years which led to wonderful growth during the 1980's.
Fast forward to 2008 during the financial crisis brought on by many factors but among them proprietary trading at the largest banks in the US (which is trading by banks using leverage to enhance earnings).
The Volcker Rule which is part of the Dodd-Frank financial reform limits banks ability to make risky trades, including derivatives and leverage that do not benefit customers.
Of course, the rule which Volcker has stated would be a four page bill is still being written and debated has thousands of pages and is a hot political topic these days.
JP Morgan's loss of $2Billion reported on 5/10/12 due to trading losses in CDO derivatives will only strengthen the resolve of those that hope to curtail bank proprietary trading.