That question is deeper than it appears

.
It must be understood that the Church has received the Deposit of the Faith from her founder. She may neither add to it, or take away from it, and has the responsibility to guard it and the duty and authority to examine it and teach based on its content. In teaching (which is what the term "Magisterium" denotes, teaching authority), she is protected from teaching error in faith and morals by God the Holy Spirit.
Now I am well aware that many readers dispute the above, but before you all jump down my throat, I'm just giving the Catholic context in which to answer the question.
When the Church teaches on faith and morals, Catholic who do not follow the teaching separate themselves from full communion with the church.
The "of God" phrase is a bit loaded in this discussion environment, but the Catholic context is that the Church, in her teaching, is exercising authority given to her by Christ her founder. What particular phrase one attaches to that flows from that.
The Church is a respecter of conscience, but she recognizes that conscience, to function properly, must be properly formed, and she expects her members to form their consciences by the teachings of the Church.
Blessings,
Gerry