Before trying to sue your union, you should try to enlist the union as your ally. Speak to your union representative and immediately file a grievance as to the company's actions. Most collective bargaining agreements provide only a short window of time to file a grievance, so you must act immediately.
As for suing your union, my best advice is to forget it. While a union owes a member a duty of fair representation, requiring that the union act in a manner that is not in bad faith, arbitrary, or discriminatory, these are complicated and expensive lawsuits. The chances of finding an attorney who will do such a case on a contingency fee basis is roughly the same as finding a needle in a haystack.
Good luck to you.
Michael S. Haber is a New York attorney. As such, his responses to posted inquiries, such as the one above, are limited to his understanding of law in the jurisdiction in which he practices and not to any other jurisdiction. In addition, no response to any posted inquiry should be deemed to constitute legal advice, nor to constitute the existence of an attorney/client or other contractual or fiduciary relationship, inasmuch as rendering legal advice involves the ability of the attorney to ask appropriate questions of the person seeking such advice and to thus gather appropriate information. In addition, an attorney/client relationship is formed only by specific agreement. The purpose of this answer is to provide the questioner with general information, not to outline specific legal rights and remedies.
I am a California attorney and not eligible to give legal advice in your state. The following is information only, based on federal law and general legal principles. YOUR STATE MAY HAVE ITS OWN LAWS THAT PROVIDE SIMILAR OR GREATER PROTECTION.
I'm sorry this happened to you, especially after being laid off for such a long time. One thing to know is that your union didn't "let the company" write you up. The decision to write you up was made by the company, not the union. All the union can do is respond to an action the employer takes. Mr. Haber is correct that the way to pursue something like this is through the grievance procedure.
Unions exist to represent the workers. There is more reason to believe the union is on your side than to believe it is not. Of course, union representatives, just like politicians, may have their own agendas. And some union reps are smart and good at what they do, and others are not . . . just like with any job. Try to make it easy for the union to help get you what you want.
Mr. Haber is also correct about how difficult it is to sue a union. Most of the attorneys who know anything about this area of law are attorneys who represent unions; they often have reason to reject any case involving a suit against a union. The other group of attorneys who know this area of law are attorneys who typically represent employers. These attorneys charge by the hour and often restrict their law practice to representing companies, not individuals.
The best organization for helping union employees without have difficulty with their unions is the Association for Union Democracy in New York. The web site is: http://aud2.uniondemocracy.org/
There is a six month statute of limitation (time limit) to pursue a claim against a union.
*** All legal actions have time limits, called statutes of limitation. If you miss the deadline for filing your claim, you will lose the opportunity to pursue your case. Please consult with an experienced employment attorney as soon as possible to better preserve your rights. *** Marilynn Mika Spencer provides information on Avvo as a service to the public, primarily when general information may be of assistance. Avvo is not an appropriate forum for an in-depth response or a detailed analysis. These comments are for information only and should not be considered legal advice. Legal advice must pertain to specific, detailed facts. No attorney-client relationship is created based on this information exchange. *** Marilynn Mika Spencer is licensed to practice law before all state and federal courts in California, and can appear before administrative agencies throughout the country. She is eligible to represent clients in other states on a pro hac vice basis. ***