When a person rejects the Faith, they are no longer a member. They can regain membership, by conversion, but sins of heresy, schism, etc make one a non-member. So says Pope Leo XII
Let me correct this for you:
When a baptised Catholic rejects the Faith, he sins. He can loose the sin by going to confession and doing the penance he is told to do.
Q. 49. Say the Apostles’ Creed.
A. I believe in God, the Father Almighty, Creator of heaven and earth; and in Jesus Christ, His only Son, our Lord; who was conceived by the Holy Ghost, born of the Virgin Mary, suffered under Pontius Pilate, was crucified; died, and was buried. He descended into hell: the third day He arose again from the dead: He ascended into heaven, sitteth at the right hand of God, the Father Almighty; from thence He shall come to judge the living and the dead. I believe in the Holy Ghost, the Holy Catholic Church, the communion of Saints,
the forgiveness of sins, the resurrection of the body, and the life everlasting. Amen.
Q. 50. What is a creed?
A. A creed is a summary or list of the chief truths we believe or profess to believe. It is a compendium of doctrine.