I also used to think, mistakenly, that priestly celibacy is equivalent to marriage vows. But that’s not the case, as Brother JReducation explained on another thread, when Fr. Alberto Cutie a famous Catholic priest and media celebrity recently left the Catholic Church in order to marry. Validly exchanged marriage vows are binding for life, no matter what (well there are declarations of nullity, but those are findings that the vows were not validly exchanged in the first place). Roman Catholic priests, on the other hand, make a “promise” to stay celibate, and a “promise” is a lesser thing than a vow. The one thing that’s a vow that cannot ever be revoked, is what consecrated religious brothers (monks) and sisters (nuns) make - the vows of poverty, chastity, and obedience. In this sense, being a consecrated religious is the equivalent of being married, because the Church has no authority to give a dispensation to a monk or nun, to go and marry. But for a priest to make the promise of celibacy, is not equivalent to the forever binding vows of married people or religious brothers and sisters (there are also priest-monks who never can obtain dispensation to marry, but not because they are ordained as priests, rather because they also happen to be consecrated religious brothers, or monks for short). There are cases when Roman Catholic priests get dispensations to get laicized and get married. And Eastern Catholic Churches do have married priests. Also, an Anglican or Lutheran person who’s already married, may convert to Catholicism and get validly ordained as a Roman Catholic priest and stay married at the same time.
The celibate priesthood is an issue of “Church discipline” in the Roman Catholic Church, which is also a manner to say that it could even be changed tomorrow and all priests could get permission to marry, if the Church decided so - because the Church has authority to make up rules in matters of discipline. But allowing validly married people to break their vows, and ordaining women priests for another example, are things that the Church has no authority to do, because these things were set by God himself as forever binding laws.
And another thing I learned, a laicized priest or a priest who leaves the Catholic Church, gets married and converts to the Episcopal Church, is still a priest forever. He can still consecrate the Eucharist, but he is forbidden to do so. Masses celebrated by such priest, and sacraments performed by him would be valid, but illicit.