Ratifier (noun)

A person or organization who formally approves or confirms a treaty, agreement, or other legal instrument.

Origin:

Mid 17th century: from ratify + -er.

Examples:

1. The United States Senate was the ratifier of the treaty.
2. The treaty needed the ratifier of at least two-thirds of the member states to take effect.
3. The ratifier of the treaty was responsible for ensuring its implementation.
4. The ratifier of the agreement was the head of state.
5. The treaty was finally ratified by the required number of ratifiers.