Utility Workers Union of America
AFL - CIO Local 127

While the decision whether to hold meetings may be left to the discretion of a union, a different rule applies as to holding elections for union officers and conducting a referendum on dues increases or other financial assessments of members.  At least for unions covered by the U.S. LMRDA (Labor Management Reporting and Disclosure Act), there are detailed requirements dealing with the frequency of elections for union officers at all the various levels of a union, and how those elections must be conducted (including requirements as to types of balloting—on the jobsite, by mail, and so forth).  At the local level, your union must provide for election of officers by secret ballot, and it must do so no less frequently than every three years.
—Adapted from The Union Member's Complete Guide, by Michael Mauer