As regulators begin final deliberations on the so-called Volcker Rule, treasurers and their financial service providers mostly see the sky about to fall after a recent analysis showed costs to use financial products from bonds to foreign exchange contracts would increase significantly. The sky did nearly fall in late 2008, however, when Lehman Brothers' collapse threatened a domino effect across Wall Street, which leaves regulators to decide which outcome is worse.

Formally known as Restrictions on Proprietary Trading and Certain Interest in, and Relationships With, Hedge Funds and Private Equity Funds, the Securities and Exchange Commission's proposal—nicknamed for its most esteemed supporter—drew thousands of comments by the Feb. 13 deadline. The majority support the provision, including those from former Federal Reserve Chairman Paul Volcker and the California Public Employees' Retirement System (Calpers), arguing that the increased costs are warranted to prevent future financial crises.

The hundreds of critical letters, mostly from financial institutions, repeat one or more of nine likely unintended consequences described by Anthony Carfang, co-founder of consultancy Treasury Strategies, in testimony before two U.S. House financial subcommittees in January. The list includes reduced access to credit, higher costs and less funding certainty for borrowers, prompting companies to structure their balance sheets more conservatively, a potential drag on a still struggling economy.