Ahead of the Thanksgiving holiday, long-simmering tensions between Wal-Mart and union organizers have come to a head as Wal-Mart seeks legal action against a labor union – a rare move for the Nation’s largest retailer, which has successfully fended off union battles in the past.

Wal-Mart Stores, Inc. has filed an unfair labor practice charge (“the Charge”) with the National Labor Relations Board (“NLRB”) – the company’s first such move in a decade – against the United Food and Commercial Workers Union (“UFCW”), which represents more than one million workers, including many workers at retailers that compete with Wal-Mart.  The filing of a charge with the NLRB, according to NLRB protocol, represents the initiation of an unfair labor practice case, after which point an investigation into the allegations is launched by labor officials.

The Charge accuses UFCW of violating the National Labor Relations Act (“NLRA”) by inappropriately picketing, trespassing on company property, intimidating customers and employees, and organizing mass demonstrations in collusion with affiliated organizations and subsidiaries.  Among those affiliated organizations that the Charge cites is the Organization for Respect at Walmart (“OUR Walmart”), a coalition of thousands of Wal-Mart workers that was formed in 2010 with financial backing from UFCW, and which was a subsidiary of UFCW up until recently.

Not coincidentally, Wal-Mart filed the Charge last Thursday evening – the same day that OUR Walmart announced plans to hold hundreds of protests at Wal-Mart stores across the country on Thanksgiving week, culminating in massive protests on Black Friday, which is one of Wal-Mart’s busiest shopping days.

Wal-Mart alleges that these protests are illegal because under the NLRA, a union seeking recognition can picket for a maximum of 30 days.  After 30 days, it must either stop picketing or take a formal unionization vote.  Wal-Mart says that UFCW is behind the protests, and that it has exceeded the 30-day limit.  OUR Walmart maintains, meanwhile, that this week’s actions are not aimed at receiving union recognition, but, rather, at protesting what it says are unfair labor practices at Wal-Mart, including low wages, poor working conditions, and retaliation against workers who speak out against such issues.

With Black Friday looming, Wal-Mart requested in its Charge that the NLRB, which is tasked with refereeing disputes between private-sector employers and employees, conduct a preliminary investigation of the allegations, and that the investigation be granted priority over other cases.  The Charge goes on to request that if the NLRB finds during its investigation that the Charge has merit, that the NLRB seek immediate injunctive relief on behalf of Wal-Mart, per the NLRA’s requirement that the NLRB seek a federal court injunction against illegal picketing.  If the NLRB decides to seek injunctive relief, a district court judge will determine whether to grant the injunction.

Since the Charge was filed, federal labor officials have said that they are prioritizing this case over nearly all other cases, explaining that charges that assert illegal picketing – as Wal-Mart’s Charge does – take priority over other labor board cases under federal labor law.  The NLRB states that its targeted responding time to such requests is 72 hours, though the agency has yet to respond as of posting time, due to what NLRB officials say is the highly complex nature of the allegations.

Indeed, given the complexity of the case, it may take weeks for the NLRB to act, making it unlikely that Wal-Mart could obtain an injunction by Black Friday – a fact that Wal-Mart itself likely was aware of from the outset.  In filing the Charge, some experts argue, Wal-Mart’s goal may not have been to obtain an injunction by Friday per se, but rather to send a warning to employees about engaging in what Wal-Mart maintains is illegal picketing.  Underscoring this point, Wal-Mart used the word “illegal” three times in a letter that it sent to UFCW notifying the union of the filing.  In other words, filing the Charge may have been simply a strategic maneuver on Wal-Mart’s part.

At the same time, the fact that Wal-Mart had felt the need to take the situation to the NLRB in the first place reflects how seriously the company has come to view a group that it had long dismissed as a mere thorn in its side.  So, while the outcome of this particular legal challenge remains to be seen, Wal-Mart may be bracing itself for future union battles.