What Is ERISA?
The Employee Retirement Income Security Act of 1974 (ERISA)
"Under certain circumstances (described below), your pension payments after you reach normal retirement age may be suspended if you return to work. For example, ERISA permits a multiemployer plan to suspend the payment of normal retirement benefits if you return to work in the same industry, the same trade, and the same geographical area covered by the plan as when benefits commenced.
Before suspending benefit payments, however, the plan must notify you of the suspension during the first calendar month in which the plan withholds payments. The notification must give you the information on why benefit payments are suspended, a general summary and a copy of the plan's suspension of benefit provisions, a statement regarding the Department of Labor regulations, and information on the plan's procedure under which you may request a review of the decisions to suspend benefit payments. If most of this information is contained in the plan's summary plan description, the notification may simply refer to the appropriate pages of the summary plan description.
A plan that suspends benefit payments must advise you of its procedures for requesting an advance determination of whether a particular type of reemployment would result in a suspension of benefit payments. If you are a retiree and are considering taking a job, you may wish to write to the administrator of your plan to ask if your pension benefits would be suspended.
http://www.dol.gov/ebsa/publications/wyskapr.html