Why can't women be priests?

Church teaching on the ordination of only men to the priesthood finds its origins in the teaching and practices established by Christ. While He was on earth, Jesus chose men to be His apostles and He passed on authority to these men to carry out His work of preaching the good news (Luke 9:1-2) and forgiving sins (John 20:23). 
 
The Catechism of the Catholic Church explains, “The Church recognizes herself to be bound by this choice made by the Lord himself. For this reason, the ordination of women is not possible” (CCC 1577). Furthermore, the Catechism informs us that “No one has a right to receive the sacrament of Holy Orders. Indeed no one claims this office for himself; he is called to it by God” (CCC 1578). 
 
Jesus came to us on earth in the form of a man. It makes sense, then, that He chose His successors—his “representatives” on earth—to be men. 
 
Finally, though we cannot always know exactly why Christ made some of the choices He made, we do know that He did not view women as inferior to men. Christ simply made clear that this particular vocation—the priesthood—would be reserved for men. In obedience to the will of God, the Catholic Church has and will continue to follow this practice of ordaining only men to the priesthood.