The process of administering a collective bargaining unit includes two primary tasks. The first of these is to negotiate the contract that determines the conditions to which both workers and managers have to agree. (This process is repeated whenever the contract has to be renegotiated: How long a contract is in place is determined at the time that each contract is finalized.)
The second major function of the union and management leaders who administer a collective bargaining agreement is to file and address grievance is a complaint filed by a worker who is a member of the bargaining unit who believes that either an element of the union contract has been violated or that a law (such as an overtime law or one addressing workplace safety) has been violated.
An example of a grievance occurred last year when the Professional Engineers in California Government filed a grievance with the Department of Personnel Administration over the issue of forced furlough days that the state's governor had put into place because of state budgetary limitations. The union argued in its grievance that the move violated the Memorandum of Understanding between its members and the state concerning both wages and working hours. (the case is described at http://www.sacbee.com/static/weblogs/the_state_worker/2009/07/engineers-file-furlough-grieva.html)
The decertification of a union is basically the ending of a union in a particular workplace and the suspension of the contract that had been negotiated by the union and the loss of collective bargaining rights. In other words, it is the mirror image of the process of certification. Here is a description (with great apparent glee) of the decertification process -- which can only be initiated by the workers, not the management:
The right of employees to unionize -- to join together as a unit for collective bargaining with their employer -- is specifically authorized by law. But that same law not only permits employees to refuse to unionize initially, but goes one step beyond to provide a framework for "deunionization" -- the process by which a union, once it has become the elected representative of the employees, may later be removed from that position if the employees so wish. http://www.hotel-online.com/News/PR2002_2nd/Apr02_Decertifying.html
Decertification can also occur when a group of workers wishes to switch from one union to another. In this case, the existing union must be decertified before a new union can be certified. This is happening in the following case as workers try to shift unions. What is especially interesting about this case, described below, is that some workers are using this process to try to break free of both unions:
We are writing to demand that you immediately withdraw your decertification petition at our nursing homes. It was only a matter of time before your decision to file election petitions put our union and our future at risk. Now, some employers are looking to take advantage of the situation by trying to bust our union altogether. Managers and outside paid union-busters are holding mandatory group meetings and individually pressuring our union brothers and sisters to vote "no union." (http://www.seiu-uhw.org / )