WASHINGTON — Senate Democrats' decision to change filibuster rules has shifted the composition of a powerful federal appeals court, a move that could bolster the banking agencies against future industry challenges to the Dodd-Frank Act.

Lawmakers confirmed the last of three judges to the U.S. Court of Appeals for the District of Columbia Circuit late Monday, filling the final vacancy on the 11-seat bench.

The court, which has tilted conservative in recent years, is a primary battleground for lawsuits against government agency rules, including several recent appeals to the financial reform law.

While the inclusion of a few more Democratic-appointed judges does not completely tip the scales on any given case before a randomly selected three-judge panel, the change is expected to have a significant impact.

"The vector has now changed and there will be more agency wins," said James Cox, a professor of law at Duke University. "From the very get-go of lobbying for what was going to be Dodd-Frank, including what rules were adopted by the various regulatory agencies, the shotgun behind the door for the business community was a conservative, anti-regulatory bent among the majority of the DC Circuit."

Until recently, the court had an even four-four split among active judges appointed by Democratic or Republican presidents, including one judge nominated by Obama who was confirmed last summer. That number will now shift to a seven-four split in Democrats' favor, though the court also retains a handful of senior judges, a form of partial retirement, most of whom are Republican appointees.

"Generally speaking, I tend to view Democratic appointees as more sympathetic to the government side, and that would make challenges to Dodd-Frank tougher," said Oliver Ireland, a partner at Morrison Foerster.

The three new judges — Robert Wilkins, Patricia Millett and Cornelia Pillard — were at the heart of the battle over the "nuclear option," after Senate Republicans torpedoed their nominations earlier in the fall. Critics warned that the court's workload was too light to require additional judges or that Obama was trying to "pack the court," rather than focusing on the qualifications or ideological leanings of the nominees.

"Even the Republicans in the Senate didn't criticize any of these judges based on legal qualifications or merit," said Dennis Kelleher, president and chief executive officer of advocacy group Better Markets. "They were reduced to making the absurd argument that the workload of the D.C. Circuit was so low that they weren't needed."

Wilkins, who was confirmed by the Senate on Monday, was formerly a public defender and then a partner at law firm Venable. He was appointed by the White House to serve on the District Court for the District of Columbia in late 2010, where he has already presided over two key appeals to the Dodd-Frank law.

Last summer he upheld a lawsuit against an obscure Securities and Exchange Commission rule requiring manufacturers to disclose the use of products containing "conflict minerals" from the Democratic Republic of Congo. The case was then appealed to the DC Circuit, where supporters of the rule faced tough questions from two judges on the panel, both Republicans, during oral arguments earlier this month. The third judge hearing the case is the previous Obama appointee.

But Wilkins has also taken issue with banking regulators during his time on the lower court, striking down the Commodity Futures Trading Commission's position limits rule, designed to cap the number of derivatives contracts a trader can hold. Wilkins sent the rule back to the agency, arguing that the CFTC failed to determine whether position limits were necessary before imposing the cap.

The decision was viewed as a win for Wall Street, and the agency later abandoned its appeal to the D.C. Circuit, re-proposing a modified version of the rule in November.

"Frankly, I think Wilkins was dead wrong. But he wrote a 40-plus-page, detailed opinion … as to why he ruled the way he ruled," said Kelleher. "So, while I disagree with him, he made a decision that was well within the bounds of reasonableness and clearly grounded in the law."

Millett, meanwhile, joins the court from law firm Akin Gump Strauss Hauer & Feld, where she co-headed the Supreme Court practice, arguing numerous cases in front of the high court on a variety of topics. Previously, she served as a Justice Department attorney and then as an assistant to the Solicitor General under Presidents Bill Clinton and George W. Bush.

Pillard also worked for the Clinton administration as an assistant to the Solicitor General and then as a deputy assistant attorney general in the Justice Department's office of legal counsel, before becoming a tenured professor of law at Georgetown University.

Observers cautioned that it can be difficult to predict someone's judicial approach for a variety of reasons, including that the indefinite tenure of the position allows for judges to come into their own and evolve their views over time. But the decision to serve in government for an extended period of time does give some suggestion of the two judges' ideological leanings.

"The fact that you chose an agency — if you're coming out of DOJ, you've chosen to work at a discount to what the private sector would pay you," said Ireland. "You have to believe that the person believes in what the agency is doing, and if they believe in what the agency is doing, they're going to be more likely to defer to that agency and likely to other agencies — though you can't ever be entirely sure."

One big remaining question is what, if any, effect the appointment of new judges might have on the regulators themselves as they design new rules. Another powerful corollary of the Senate's decision to go nuclear is Obama's new latitude in nominating officials to head government agencies. The extent to which this, combined with more sympathetic oversight from the courts, will translate into tougher rules remains to be seen.

"It's this multi-step thing in that the regulators that the Obama administration can now appoint can be regulators that might be a bit more inclined to be a bit more aggressive. Once they are there, they can write more aggressive rules, knowing the courts are more likely to back them up," said Edward Mills, a policy analyst at FBR Capital Markets.

The D.C. Circuit has so far handed down one big loss to regulators under Dodd-Frank, on the SEC's proxy access rule. A panel of three conservative judges knocked down the rule in 2011, arguing that the agency failed to consider the economic effects of the measure, which was designed to make it easier for shareholders to get their own nominees onto corporate boards. Three Republican-appointed judges also invalidated Obama's recess appointments to the National Labor Relations Board early last year, raising concerns about Richard Cordray, whom the president nominated to head the Consumer Financial Protection Board on the same day. Cordray was ultimately confirmed as part of a Senate deal last summer, while the NLRB case now advances in the Supreme Court.

Lower court judges, meanwhile, haven't necessarily been friendly to implementation of the Dodd-Frank law either. Last year, a D.C. District Court judge struck down the SEC's resource extraction rule, which the agency has said it will rewrite, and another judge on the same court ruled against the Federal Reserve's debit card interchange fee provision. Both judges were appointed by President George W. Bush. The Fed is appealing the interchange decision in the D.C. Circuit, this time in front of two Democratic-appointed judges and one Republican-appointed judge.

Victoria Finkle is American Banker's Capitol Hill reporter.