Our plan previously described eligible beneficiaries as a "legal spouse." We have formerly allowed employees to claim common law spouses as beneficiaries. We would like to change our plan to state that only legally married spouses can be beneficiaries under the plan. How do we do this? Does is matter what the state law is? The state where the plan is administered does not recognize common law, but we have employees in another state that does recognize common law. Any help would be appreciated. Thank you.

What type(s) of plan are we talking about? pension, 401(k), health, dental, voluntary benefits, ...

Common law marriage is allowed in some jurisdictions (e.g., Texas, SC) as legal marriage. Since the state where the parties reside determines whether they are married for benefit purposes (There is no regulation on how to determine if parties are married under ERISA) the law of the state where the plan is administered is irrevalent. The Federal Defense of Marriage Act permits a state to disregard a marriage ceremony between two persons of the same sex which is performed in another state that recognizes same sex marriages.

Unclear. Does "allowed" refer to an administrative decision or to a plan provision?