The unfair labor practice charge filed this week by three Boeing South Carolina workers against the Machinists union will be difficult to prove and is unlikely to gain the same traction as the union's claims against Boeing earlier this year, according to labor law experts.

The employees alleged the International Association of Machinists and Aerospace Workers brought its charge, which led to the National Labor Relations Board lawsuit in April, to discourage Boeing and other companies from creating jobs in right-to-work states, such as South Carolina.

The retaliation charge and how it was resolved this month, following a landmark contract extension for the Machinists, violate the National Labor Relations Act, according to the complaint filed Wednesday with the NLRB.

The experts, who have followed but have not been involved in the case, said the workers' concerns have some basis and their free counsel from the National Right to Work Legal Defense Foundation will represent them well.

But, for political and legal reasons, their charge against the Machinists -- and the related request for an investigation of the judge who presided over the more famous Boeing litigation -- don't stand much of a chance.

"It's going to be a very hard one to prove, just like I thought the one against Boeing was going to be very hard to prove," said Dennis R. Nolan, the Webster Distinguished Professor Emeritus of Labor Law at the University of South Carolina School of Law.

The union's pursuit of its own self-interest -- keeping work in Puget Sound -- is not, by itself, proof of retaliation against the nonunion work force in North Charleston, Nolan said.

Kenneth T. Lopatka, who served as chief counsel to the NLRB chairman during President George W. Bush's administration, has an even dimmer view of the now-resolved case against Boeing, but that doesn't mean the union broke the law.

The workers -- Dennis Murray, Cynthia Ramaker and Meredith Going Sr. -- need hard evidence, said Lopatka. who is now in private practice in the Charleston area.

Even if the legal campaign seems a longshot, Murray said he remains committed.

"How come the NLRB seems to be upholding the rights of the union and not the rights of the nonunion workers when the (labor act) … is supposed to promote fairness and equality for all workers?" Murray asked Wednesday. "Those of us in right-to-work states … are coming up on the short end of the stick."

J. Steven Warren, a partner at Constangy Brooks & Smith in Greenville who has represented employers for 35 years, said "there's no question that the union filed a charge against Boeing initially because of South Carolina employees going union-free, at least in part." But he said other factors, including a potential "timeliness hurdle," will be difficult for the local workers to overcome.

"They'll make the strongest case they can, but they have an uphill battle," Warren said.

The next step is an investigation by the NLRB's regional director. After the case is reviewed by the agency's leadership in Washington, the board will decide whether to file a formal complaint.

That will take time, Lopatka said, for both practical and political reasons. "If this one were dismissed out of hand, it just doesn't look good," he said.

Spokesmen for the Machinists and the union's Seattle district office did not return messages this week. Attorneys at the National Right to Work Legal Defense Foundation and a representative for Boeing's local campus could not be reached.

In an email, NLRB spokeswoman Nancy Cleeland said, "our only comment on this is that we will investigate this charge just as we investigate every one of the tens of thousands of charges we receive each year."

Reach Brendan Kearney at 937-5906.