Under the Explanation to Section 4 of the Special Marriage Act, 1954, "custom" means:

The Explanation to section 4 requires a rule specified by State Government notification in the Official Gazette for the relevant tribe, community, group or family. The proviso requires long continuous uniform observance, certainty, consistency with reasonableness and public policy, and no discontinuance for a family custom. A long-standing practice alone does not satisfy this statutory definition.