A U.S. rule years in the making that was intended to restore consumers’ ability to band together to sue financial companies could unravel in just a few months as the heads of two federal agencies clash over it and critics gear up for battle.

On Wednesday, the Consumer Financial Protection Bureau’s rule abolishing “mandatory arbitration” clauses will be published in a directory of regulatory actions called the Federal Register, starting the timer for two possible ways of undoing it.

The rule bans companies from requiring customers to sign agreements when opening new accounts that they will not join a group lawsuit, or class action, in the event of a dispute. Critics say such lawsuits only benefit lawyers and that arbitration is a quick, cost-effective alternative to the courts.

Once the rule is published, anyone sitting on the council of the country’s top financial regulators can petition for a stay within 10 days by showing it significantly risks injuring the banking system. One member, Acting Comptroller of the Currency Keith Noreika, started moving toward that step after the rule’s final version was released last week.

The rule will also be open to possible nullification under the Congressional Review Act. Already powerful Senate Republicans, including Banking Committee Chairman Mike Crapo, are drafting a resolution to kill the rule. Under the Congressional Review Act, Congress could take up to six months to consider the resolution.

However, both attempts to stymie the rule could fail.

Noreika contends his office has not been able to review data used to write the rule. He and CFPB Director Richard Cordray have exchanged slightly hostile letters over the last week, and on Tuesday Cordray wrote that the CFPB is “assembling the data your staff has requested.”

Noreika replied in a statement that he would “conduct an independent review of the data and analysis in a timely manner.”

But Cordray says his agency released a thorough analysis two years ago and a rulemaking proposal more than a year ago that was accompanied by extensive research. Cordray also points out that Congress banned the arbitration clauses from mortgages and did not injure that market, casting doubt on Noreika’s safety and soundness concerns.

In the Senate, a nullification resolution could be crowded out by other, more pressing business.

A third line of attack is less bound by time. The U.S. Chamber of Commerce lobbying group may announce as soon as Wednesday, when it holds an event on arbitration, that it is suing over the rule. (Reporting by Lisa Lambert; Editing by Jonathan Oatis