Supreme Court Ends Antitrust Case Against NAR and Zillow – What Should Every Mortgage Executives Know?

The U.S. Supreme Court has declined to review a closely watched antitrust case involving Zillow Group, Inc. (Zillow) and the National Association of Realtors (NAR). By refusing to grant certiorari, on October 20, 2025, the Court effectively upheld the Ninth Circuit’s March 3, 2025 ruling that denied the plaintiff’s federal and state antitrust and consumer protection claims.  The plaintiff had appealed a loss in the U.S. District Court from the Western District of Washington.

For mortgage lenders that depend on real estate platforms for lead generation, data access, and brand visibility, this case carries valuable lessons on competition, platform control, and compliance risk.

The Underlying Claim in Brief

The dispute generally arose because a large online brokerage sued Zillow and NAR, claiming that changes to how listings appeared online unfairly harmed homes not listed on a multiple listing service (MLS).

A key issue was a design update that placed non-MLS homes in a separate “Other Listings” tab, a section that consumers were reportedly less likely to click. The brokerage argued that the marketplace’s display design, combined with a NAR “no commingling” policy (an optional rule allowing MLSs to separate listings), amounted to an illegal restraint of trade.  The plaintiff made, or failed to make, other claims as well.

The defendants generally countered that:

• The design update was an independent business decision, not a coordinated scheme.

• The NAR policy was optional, with each MLS choosing whether to adopt it.

The Underlying Decision in Brief

The Ninth Circuit, often painted in the media as business hostile, sided with Zillow and NAR, finding no evidence of coordinated anticompetitive behavior. Key findings included:

• The “no commingling” policy’s optional nature undermined any claim of a unified conspiracy.

• The marketplace’s design shift was an independent, competitively motivated decision, not part of a collusive plan.

• A last-minute argument that the marketplace conspired with specific MLSs was waived because it had not been raised in the court below.

The Ninth Circuit also upheld jury instructions permitting the defendants to argue that their conduct reflected reasonable business practices under state deceptive trade laws.

The Ninth Circuit’s decision is unpublished so of limited precedential value.

With the Supreme Court declining review, this ruling is now final.

Why It Matters for Mortgage Executives

The ruling is, of course, a great victory or loss for the parties involved in the immediate term. 

Perhaps more importantly, however, is that the ruling underscores how platform design, data visibility, and consumer interface choices can trigger litigation, and how courts might evaluate these issues under antitrust and consumer protection frameworks.  These issues likely will continue to flare in courts given that other recent antitrust and similar cases have been making headlines.

For the mortgage industry, key questions may include:

1.        Understand Platform Dependencies

What should mortgage companies consider when relying on major platforms? 

• Who controls visibility?

• How do algorithms rank or display products?

• How can platform design influence consumer behavior?

2.        Document Business Rationale

What documentation can help provide protection if platforms or related business decisions are challenged as platforms and users create or make changes to customer-facing tools?

3.        Evaluate Antitrust, UDAAP and Other Regulatory Risk

Even when there is no conspiracy, do lenders open themselves up to attack for such things as:

• Display decisions?

• Data-sharing practices?

• Price-fixing?

• Rankings or sorting algorithms?

Lenders must assess these risks proactively.

4. Monitor Platform Partnerships

Digital aggregators and marketplaces are under increased scrutiny. Mortgage executives should be aware that:

• Visibility practices may be challenged.

• Data provided by, or to, platforms may become part of antitrust and other claims by regulators or private plaintiffs, including competitors.

• Courts seem to be looking closely at how competitive advantage is created through design.

Bottom Line

The Supreme Court’s decision ends this high-profile antitrust battle, but the implications may extend far beyond this case. For mortgage leaders, the case is a reminder that online visibility, platform governance, and consumer perception are emerging compliance hotspots.

Mortgage companies should take stock of their platform partnerships now, ensuring these relationships, and the design decisions behind them, are grounded in clear, compliant, well-documented business strategy.

Need Strategic Guidance?

If you want help reviewing your platform relationships, compliance posture, or antitrust exposure, contact troy@garrishorn.com.