Federal law as defined in ERISA governs multi and single employer pension plans. As long as you are vested in your pension, as defined in the plans documents, you are entitled to whatever benefits you have accrued.
There are two types of vesting schemes. One is five year cliff vesting. If you are on the job and meet all the minimum working criteria as defined in the pension plan documents you are vested in all you benefits after five years.
In a step vesting scheme you have vested in a percentage of your benefits for each year, with 100 percent vesting occuring no later than the 7th year.
Your benefits are guaranteed, must likely, by the pension benefit guarantee corporation in the event that the plan does not have the money to pay you your vested monthly benefit upon retirement.
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