July 25 1968 Pope Paul VI published his Encyclical letter Humanae Vitae.
His commissions, set up in response to the development of oral contraceptives in the 60s, came out more than 2/3 in favour of accepting such contraceptives amongst the bishops, and more than ¾ in favour amongst theologians and other specialists.
Pope Paul VI rejected the advice of his commission because this did not come to the conclusion that he did.