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Wal-Mart Stores Inc has sued a major grocery workers union and others who have protested at its Florida stores, the latest salvo in its legal fight to stop "disruptive" rallies in and around its stores by groups seeking better pay and working conditions.

Wal-Mart does not have union-represented workers in its U.S. stores. Nevertheless, it has long faced opposition from various labor groups including the United Food and Commercial Workers International Union (UFCW), and from a small but vocal group of current and former employees backed by the union and known as OUR Walmart.

The lawsuit filed on Friday in Orange County, Florida state court seeks "to help protect our customers and associates from further disruptive tactics associated with their continued, illegal trespassing," Walmart spokesman Dan Fogleman said.

Defendants, however, charged that the world's biggest retailer is trying to muzzle its critics.

"This is another attempt on Wal-Mart's behalf of ... silencing their employees and also the communities that support them," Denise Diaz, executive director of Central Florida Jobs With Justice Corp and a defendant named in the suit, said before reviewing the documents.

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"Rather than creating good jobs with steady hours and affordable healthcare, Walmart's pattern is to focus its energies on infringing on our freedom of speech," the Organization United for Respect at Walmart (OUR Walmart), also a defendant, said in a statement.

Other defendants include the 1.3 million-member UFCW and the individuals Angela Williamson, Alex Rivera, and Alan Hanson.

The UFCW was not immediately able to comment on the lawsuit.

Wal-Mart alleged that the defendants violated Florida law through coordinated, statewide acts of trespass in several Walmart stores over the last eight months. It has asked the court for a legal ruling that would prevent future trespassing.

In the lawsuit Wal-Mart cited an example where a group of protesters projected a video promoting OUR Walmart on the side of a store in Orlando and passing out literature inside that store in July, 2012.

It alleged that a group of UFCW demonstrators returned to that same store on October 30, 2012 and "confronted the store manager and handed him a rotten pumpkin painted in support of OUR Walmart. The group left the store only after the manager warned that he had called the police."

Wal-Mart filed an unfair labor practice charge against the UFCW in November, asking the National Labor Relations Board to halt what the retailer said were unlawful attempts to disrupt its business in several states including protests that were planned for Black Friday, the busy shopping day right after Thanksgiving. In January, labor groups said that they would stop much of their picketing against the chain, while still trying to push the company to improve working conditions.

The case is Wal-Mart Stores Inc v. United Food and Commercial Workers International Union et al, 9th Judicial Circuit Court of Florida, Orange County, No. 2013-CA-004293.

Reporting by Jessica Wohl in Chicago and Lisa Baertlein in Los Angeles.