Two large healthcare staffing firms appear set for a new court fight. Aya Healthcare accused AMN Healthcare (NYSE: AMN) of attempted monopolization and restraint of trade in a lawsuit filed last Thursday in federal court.

In its complaint, Aya argues AMN uses uncompetitive practices to restrict the available supply of medical travelers and prevent rivals from competing.

“Defendant is the dominant seller in its markets and apparently believes that the best way to get ahead, stay ahead and improve profit margins is to prevent its rivals from competing against it, while suppressing the pay and available opportunities of its own employees,” according to the complaint.

AMN ranks as the largest US healthcare staffing provider; Aya is the ninth-largest provider, according to Staffing Industry Analysts’ research. Both are based in San Diego, Calif.

In a statement today, AMN responded to the lawsuit.

“A workforce solutions and staffing competitor has filed a meritless lawsuit that relies on distortion of fact and law,” AMN said. “We are confident that the courts will uphold our practices and policies, and the disingenuous nature of these allegations will be revealed. AMN Healthcare is proud to operate with the highest ethical and legal standards. We are not immune to lawsuits from vendors, former business associates and employees whom we hold accountable to our same standards.”

The company also said “AMN Healthcare is a trusted partner to our clients providing strategic workforce solutions such as managed services programs and vendor management system technologies. These solutions have proven to deliver significant customer value and efficiency and have broad adoption in multiple industries across the world.”

Aya presented its allegations in a 64-page complaint. They include “no-poaching” agreements where healthcare staffing firms supplying medical travelers (nurses and technicians) through AMN on a subcontracted basis agree not to hire any AMN employees in perpetuity. Such agreements hurt competition, Aya argues. In addition, it claims AMN is overbroad in its definition of employees, including medical travelers who have no pending assignments. It also argues AMN misclassifies as trade secrets even the names of employees when many are known to professionals in the medical-traveler market and can readily be identified on social media sites.

The complaint says AMN also requires its internal recruiters to sign “no-poaching” agreements where they agree not to solicit AMN employees for between one year to 18 months from the time they leave AMN, according to the complaint. The complaint argues this hinders competition for internal employees.

The companies have locked horns before. In 2015, AMN sued Aya and four of its former recruiters in San Diego County Superior Court. The suit claimed the recruiters breached their nonsolicitation agreements and misappropriated trade secrets and other confidential information.

However, a judge ruled Jan. 26 that AMN’s confidential nondisclosure agreement was unenforceable under California law, according to court records. It also prohibited AMN from enforcing employment agreements in California that restrict former employees from soliciting other employees of AMN.

In the lawsuit filed last week, Aya also claims AMN asked it to sign a contract, which Aya believed was unlawful, whereby the companies would agree not to hire one another’s employees. Aya said it rejected the offer twice.

In addition, Aya contends AMN locks down markets by signing hospitals and networks to exclusive-provider contracts, one example of which being the San Francisco Bay Area, according to the complaint. And subcontracting staffing firms can’t charge discount prices to attract more business or distinguish themselves to hospitals because they are prohibited from contacting hospitals directly.