Utility Workers Union of America
AFL - CIO Local 127

Depending on the law covering your type of workplace, subjects of bargaining may be:
•    “Mandatory,” meaning that the parties must bargain over them if either side wants to.  Covered topics are those dealing with “wages, hours and other terms and conditions of employment,” including health plans, pensions, leave policies and so on.
•    “Permissive” or “voluntary,” meaning that either side has the right to decide not to bargain over that subject.  Examples might be a proposal to change which employees are covered by the collective bargaining agreement.
•    “Non-negotiable” or illegal, meaning that the collective bargaining agreement cannot address that topic at all.  The parties to a contract, for example, couldn’t legally bargain over whether or not only union members can be hired.
-- Adapted from The Union Members Complete Guide, by Michael Mauer