I'm afraid he's gotcha this time, BD. You're probably thinking of verses like:
Lev. 12:1-4 : 1 The LORD said to Moses, 2 "Tell the Israelites: When a woman has conceived and gives birth to a boy, she shall be unclean for seven days, with the same uncleanness as at her menstrual period. 3 On the eighth day, the flesh of the boy's foreskin shall be circumcised, 4 and then she shall spend thirty-three days more in becoming purified of her blood; she shall not touch anything sacred nor enter the sanctuary till the days of her purification are fulfilled. (NAB, i.e. the "Catholic" approved Bible)(Emphasis added)
Now granted, this language is very confusing, and who among us could possibly make the correct interpretation of it without being told by the Magisterium. However, to understand their logic, as it is being explained to us, perhaps an illustration would be helpful. The Law says that "Thou shalt not commit adultery" (Ex. 20:14). BUT, and this is very important, NO WHERE in scripture does it say that one shall not commit adultery on a Tuesday. Therefore, if the Magisterium declared that adultery on Tuesdays was fine, then they would be exactly in accordance with scripture. I hope this was of some service to you in understanding how the Magisterium works.
-A8
Just so I understand at least some of the Protestant positions on this matter, I am assuming that at least the followers of Luther and Calvin accept the canons of the Fifth Ecumenical Council and particularly:
"If anyone shall not confess that the Word of God has two nativities, the one from all eternity of the Father, without time and without body; the other in these last days, coming down from heaven and being made flesh of the holy and glorious Mary, Mother of God and always a virgin, and born of her: let him be anathema." Canon II
"IF anyone shall not call in a true acceptation, but only in a false acceptation, the holy, glorious, and ever-virgin Mary, the Mother of God, or shall call her so only in a relative sense, believing that she bare only a simple man and that God the word was not incarnate of her, but that the incarnation of God the Word resulted only from the fact that he united himself to that man who was born [of her];(1) if he shall calumniate the Holy Synod of Chalcedon as though it had asserted the Virgin to be Mother of God according to the impious sense of Theodore; or if anyone shall call her the mother of a man (Anthropotokon) or the Mother of Christ (Xristotokon), as if Christ were not God, and shall not confess that she is exactly and truly the Mother of God, because that God the Word who before all ages was begotten of the Father was in these last days made flesh and born of her, and if anyone shall not confess that in this sense the holy Synod of Chalcedon acknowledged her to be the Mother of God: let him be anathema." Canon VI
Now, it seems pretty clear that those who deny the perpetual virginity of the Most Holy Theotokos are anthemized by The Church and have been since the 500s.