(My response assumes you work in the private sector, not the public sector.)
I'm not sure I even understand this! With who or what agency did the BA file charges, and what kind of charges? What were the allegations in the charge? When you say "on behalf of the client," do you mean under the client's name, as representative of the client, or what? And who is "us"? (I'm not suggesting you respond to these questions here on Avvo. Avvo is a public web site and anyone can read what you post here, including the union, the employer, and the rest of the world.)
You should look at your union bylaws and constitution. There might be something in there that says no union member shall take any action against the interest of the union . . . I can see an argument that what you did interfered with CBA negotiations, but such an interpretation would most likely be in violation of the Labor-Management Reporting and Disclosure Act, 29 U.S.C. §§ 401 et seq. (LMRDA) (aka Landrum-Griffin Act) as well as OSHA laws.
That same bylaw provision may provide an opportunity for you to file charges against the BA.
You would be well advised to consult with an attorney before you proceed, and to do so very quickly before any time limits run out. If there are enough of you involved, you can share the cost so it won't be too oppressive for any one of you to fund.
It may be difficult to find an attorney who knows union law and also assists union members in cases against unions, because most attorneys who know anything about unions either represent unions, so are unlikely to take a case against a union, or are anti-union right-wingers who want to bust unions and destroy the only tool working people have to counter management excess. The good thing is that because you are dealing with federal law, you are probably able to use an attorney in any state.
A good source for information about the rights of union members is the Association for Union Democracy: http://aud2.uniondemocracy.org/.
@MikaSpencer * * * twitter.com/MikaSpencer * * * PLEASE READ: 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.