Article XI, Section 18

The historical institution and legal contract solemnizing the relationship of one (1) man and one (1) woman shall be the only legally recognized marital contract in this state. Any policy or law or judicial interpretation, purporting to define marriage as anything other than the historical institution and legal contract between one (1) man and one (1) woman, is contrary to the public policy of this state and shall be void and unenforceable in Tennessee. If another state or foreign jurisdiction issues a license for persons to marry and if such marriage is prohibited in this state by the provisions of this section, then the marriage shall be void and unenforceable in this state.