29 U.S.C. § 1161: Plans must provide continuation coverage to certain individuals

(a) In generalThe plan sponsor of each group health plan shall provide, in accordance with this part, that each qualified beneficiary who would lose coverage under the plan as a result of a qualifying event is entitled, under the plan, to elect, within the election period, continuation coverage under the plan. (b) Exception for certain plansSubsection (a) shall not apply to any group health plan for any calendar year if all employers maintaining such plan normally employed fewer than 20 employees on a typical business day during the preceding calendar year.