He will not be barred from the sacraments, but intellectually he might stumble with struggling with teachings in the Catholic faith as it’s not always as clear how they are confirmed by scripture. I really like this scripture quote for helping people move beyond using ‘just the bible’ to know about the mysteries of God,
““I have yet many things to say to you, but you cannot bear them now. 13 When the Spirit of truth comes, he will guide you into all the truth; for he will not speak on his own authority, but whatever he hears he will speak, and he will declare to you the things that are to come.”
There are certain mysteries, called Private Revelations, which are not found in the Protestant Churches. Bible base Churches would answer this saying that the Holy Spirit will reveal to us small things like; prophecies, speaking in tongues, and the other spiritual gifts. However, it this isn’t an adequate answer, because there were more miracles going on during the early church than today, and there must be something else that was difficult for those early Christians to bear. As for the case with Private Revelations, Catholics are not required to believe them as oftentimes, we ‘cannot bear them now.’ Things like the Rosary, the Sacred Heart of Jesus, the Immaculate Heart of Mary, are some examples of these Private Revelations the Holy Spirit has revealed to the Church. If he was strongly practicing in the Protestant Church for a long period of time, he may struggle with things like Mary, purgatory, etc. as it is not so clear where these teachings regarding these things are in the bible.
I really also like this imagery for explaining some of these deeper mysteries in the Catholic faith. This is how God revealed the secrets of Mary to the Venerable Mary of Agreda, who’s body remains incorrupt to this day.
“Presently I saw a most precious veil covering a
treasure and my heart burned with desire to see it raised
and to look upon the sacred mystery which I understood
was hidden beneath. My desire was answered in the fol
lowing manner:” “;Obey, O soul, in what was enjoined
and commanded thee ; despoil thyself of thyself, and then
this mystery will be revealed to thee.”;
Words of Jesus to Venerable Mary of Agreda