"Tu es sacerdos in aeternum, secundum ordinem Melchisedech" -- "Thou art a priest forever, according to the order of Melchizedek" (Ps. 109.4 = 110.4 KJV).
The most that can be done to a man who has been properly ordained a priest is to strip him of the right to exercise priestly functions. That was done to at least one of the Boston area pedophiles.
even if he became a priest under false pretenses? interesting.