How the Roman Catholic Church chooses to decide who is—and who is not a Roman Catholic—is up to that church. Even so, this is quite a story (from Reuters):
Liberal and conservative Roman Catholic activists in Germany criticised a decree that came into effect on Monday to deny sacraments and religious burials to people who opt out of a “church tax”.
The German bishops issued the decree last week warning Catholics who stop paying the tax they would be excluded from all religious activities, also including working in a church job, becoming a godparent or taking part in parish activities.
“‘Pay and pray’ is a completely wrong signal at the wrong time,” the reformist movement We Are Church said on Monday. The decree “shows the great fear of the German bishops and the Vatican about further serious losses in church tax revenue.”
A conservative group called the Union of Associations Loyal to the Pope asked why Catholics who stop paying the tax would be punished but those it called heretics could stay in its ranks.
“So sacraments are for sale – whoever pays the church tax can receive the sacraments,” it said in a statement, saying the link the decree created “goes beyond the sale of indulgences that (Martin) Luther denounced” at the start of the Reformation.
German tax offices collect a religious tax worth 8 or 9 percent of the annual regular tax bill of registered Catholics, Protestants and Jews and channel it to those faiths. An official declaration that one is leaving the faith frees the citizen from this tax….