Under which amendment was the status of Ahmadis declared as 'Non-Muslim'?

Under which amendment was the status of Ahmadis declared as 'Non-Muslim'?

کس ترمیم کے تحت احمدیوں کی حیثیت کو 'غیر مسلم' قرار دیا گیا؟
Explanation

Ahmadis are considered non-Muslims by many mainstream Muslims.

Mirza Ghulam Ahmad founded this movement.

In 1974, the Pakistani government enacted the 2nd Amendment to officially declare Ahmadis as non-Muslims.

Pakistan is the only country in the world to do so.