But the power to bind and lose has been granted to the Church, specifically in the office of the pope, by Christ.
Matthew 16
18 And I tell you, you are Peter, and on this rock I will build my church, and the powers of death shall not prevail against it.
19 I will give you the keys of the kingdom of heaven, and whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven."
The pope is not just a man when speaking on matters of Faith and Morals.
Just some paragraphs of the Catechism. I suggest that you get a copy and read it.
2034 The Roman Pontiff and the bishops are “authentic teachers, that is, teachers endowed with the authority of Christ, who preach the faith to the people entrusted to them, the faith to be believed and put into practice.” The ordinary and universal Magisterium of the Pope and the bishops in communion with him teach the faithful the truth to believe, the charity to practice, the beatitude to hope for.
2035 The supreme degree of participation in the authority of Christ is ensured by the charism of infallibility. This infallibility extends as far as does the deposit of divine Revelation; it also extends to all those elements of doctrine, including morals, without which the saving truths of the faith cannot be preserved, explained, or observed.
2036 The authority of the Magisterium extends also to the specific precepts of the natural law, because their observance, demanded by the Creator, is necessary for salvation. In recalling the prescriptions of the natural law, the Magisterium of the Church exercises an essential part of its prophetic office of proclaiming to men what they truly are and reminding them of what they should be before God.
2037 The law of God entrusted to the Church is taught to the faithful as the way of life and truth. The faithful therefore have the right to be instructed in the divine saving precepts that purify judgment and, with grace, heal wounded human reason. They have the duty of observing the constitutions and decrees conveyed by the legitimate authority of the Church. Even if they concern disciplinary matters, these determinations call for docility in charity.