Why five agencies had to vote on the Volcker Rule

The Volcker Rule, a creation of the 2010 Dodd-Frank financial regulation overhaul, faced its last step before taking effect on Tuesday, when five federal regulatory agencies voted on its approval.

That it took five agencies, with a total of 22 voting members, to approve the law is a reflection of the way regulation works in the U.S. and a hint to understanding why it took three years for regulators to finish writing the rule.