Wal-Mart Files With N.L.R.B. to Block Union-Backed Protests For years, Wal-Mart has fended off repeated efforts by unions and their supporters to organize its workers. Now, that battle is once again escalating. In a rare move, Wal-Mart is trying to stop a union-backed group from staging a series of demonstrations against the company on Black Friday, the busiest shopping day of the year. Wal-Mart Stores, the nation's largest employer and retailer, has filed a complaint with the National Labor Relations Board - its first in a decade - seeking to prevent the group, known as OUR Walmart, from holding what the group says will be the biggest protests of this kind against the company at hundreds of stores. Wal-Mart called the protests planned for this week a union-financed, union-orchestrated effort that did not represent how most employees felt. It said it expects small protests at just a few stores. It is unclear how widespread employee support for OUR Walmart is; previous, smaller protests so far have been a mix of employees as well as union and community supporters. Labor experts caution that the complaint, filed on Thursday, could be meant as a warning shot to discourage workers from participating since the labor relations board often takes months to make a ruling, but it nonetheless reflects how seriously the company has come to view a group that it had once dismissed as a nuisance. William B. Gould IV, a Stanford University law professor and chairman of the labor board under President Bill Clinton, said the protests were more about employment conditions and retaliation against employees than a unionization drive. "I don't see this translating into a great deal of success in terms of unionizing Wal-Mart or in terms of being particularly effective in improving conditions," Mr. Gould said. But I must say if they've gone to the N.L.R.B. on this, that must show that Wal-Mart is really concerned. Since October, OUR Walmart has staged smaller strikes at individual stores, though none of those disrupted Wal-Mart's operations, the company said. OUR Walmart said that last month 88 workers at 28 stores did not report to work, in a job action. OUR Walmart has also flown dozens of workers to Wal-Mart's headquarters and is encouraging religious leaders to hold a "Black Friday Prayer Vigil" to object to the company's treatment of workers. Wal-Mart had initially brushed off these actions as inconsequential public relations efforts. But it is taking them more and more seriously, sending a memorandum advising managers how to deal legally with protesters and warning some union-friendly groups that they might face arrest if they trespass during the protests. All this points to an increasingly fierce contest between Wal-Mart and labor groups that are bent on mobilizing and organizing the company's work force, with a near-term goal of pressing for higher wages and a longer-term goal of emboldening workers to demand a union. "You are going to see unprecedented activity from now and going into Black Friday," said Dan Schlademan, a principal organizer of the events and director of Making Change at Walmart, an affiliate of the United Food and Commercial Workers Union. The food and commercial workers union has made Wal-Mart a target because the company has helped put many unionized supermarkets out of business and helped push down wages at many competitors. Wal-Mart, moreover, has vigorously resisted unionization drives, closing a store in Canada after workers there voted to unionize and arranging to have outside suppliers provide prepackaged meat after the butchers at a store in Texas voted to unionize in 2000. The food workers union has been spending heavily on this push, paying more than $50,000 for hotel rooms near Wal-Mart's headquarters last year when it sent employees and representatives to company events, according to a filing with the Labor Department. In this week's planned events, OUR Walmart, which stands for Organization United for Respect at Walmart, is enlisting a broad range of allies, arranging fliers and letters that community, church and civil rights groups can use to publicize the Black Friday protest. OUR Walmart has even prepared remarks that it is suggesting members of the clergy might use in prayer, "to call upon the world's largest corporation to treats its workers with justice and fairness." Many of those workers assert that Wal-Mart pays poverty-level wages, assigns too few hours a week and retaliates against protesting employees.