When it comes to the new fiduciary rule for retirement plan advisors issued by the Department of Labor, “final rule” may not be final, warn its advocates.

Both Tom Perez, the labor secretary, and Sen. Elizabeth Warren, founder of the Consumer Financial Protection Bureau, warn that the rule still faces withering assaults in the courts and Congress by Wall Street firms and their representatives.

“There still may be more fights to come,” Warren said in a speech in Washington Wednesday.

Considering the rule could cost Wall Street $17 billion a year, she said there are plenty of reasons for financial firms to dig in their heels and into their wallets to pay for high powered lobbyists and corporate litigators.

Sen. Cory Booker, a New Jersey Democrat, told the same audience that rules have been attacked and undermined before.

Meanwhile, in a joint press release, two Republican leaders said they would keep using the tools at their disposal to fight a fiduciary rule out of concern it would keep low- and moderate-income Americans from receiving financial advice and hamper the ability of small businesses to offer their workers retirement savings options.

The two Republicans—John Kline, who chairs the House Education and the Workforce Committee, and Phil Roe, chair of the Pensions Subcommittee—have held numerous hearings on the conflict of interest standard and introduced legislation to stop it. They have promised their attacks will continue.

House Speaker Paul Ryan has made a similar pledge.

Bark, yes. Bite, maybe not.

Though loud, repeated attacks against Obamacare and the Dodd-Frank Act in Congress and the courts have resulted in some weakening of the laws, the rules and the bureaucracies put in place to administer and enforce these laws have generally stood. Dozens of bills to undermine both have been introduced with the knowledge of their sponsors that the measures have no chance of becoming law.