Germany's Roman Catholics can only remain part of the Church if they pay a membership tax, a court has ruled.
All Germans who are officially registered as Catholics, Protestants or Jews pay a religious tax, worth an extra 8-9% of their income tax bill.
This had been challenged by a retired law professor who said he wanted to remain a Catholic but not pay the tax.
Last week, a new bishops' decree warned that anyone not paying the tax would be denied the right to religious rites.
The German church levy was introduced in 1803 in compensation for the nationalisation of religious property.
In 2011, the Catholic Church received 5bn euros (£4bn; $6.4bn) and the Protestant Church 4.5bn euros from taxpayers, each adding up to the bulk of the churches' income, the BBC's Berlin correspondent Stephen Evans said.
He added that this arrangement, whereby the state collects taxes on behalf of religious groups and then reimburses them, was unusual in Western secular societies.
Alarm over decline
Hartmut Zapp, a retired professor of church law, filed a legal challenge in 2007, arguing that under Catholic doctrine, Church membership was determined by a person's beliefs and not by a financial relationship.
The Freiburg University academic said he wanted to continue praying and receiving Holy Communion without paying the religious levy.
Judges at the Leipzig Federal Administrative Court, however, disagreed with Prof Zapp and ruled that there could not be partial Church membership.
Their verdict follows a new bishops' decree issued last week, according to which anyone failing to pay the tax will no longer have the right to Holy Communion and religious burial.
Already alarmed by declining congregation numbers, the bishops were also pushed into action by Mr Zapp's legal challenge.
They said refusal to pay Church tax should be seen as a serious act against the community.
Catholics make up around 30% of Germany's population but the number of congregants leaving the church swelled to 181,000 in 2010, with the increase blamed on revelations of sexual abuse by German priests.
"This decree makes clear that one cannot partly leave the Church," Germany's bishops' conference said last week, in a decision endorsed by the Vatican.
Unless they pay the religious tax, Catholics will no longer be allowed receive sacraments, except before death, or work in the church and its schools or hospitals.
Without a "sign of repentance before death, a religious burial can be refused", the decree states. Opting out of the tax would also bar people from acting as godparents to Catholic children.
"This decree at this moment of time is really the wrong signal by the German bishops who know that the Catholic church is in a deep crisis," Christian Weisner from the grassroots Catholic campaign group We Are Church told the BBC.
But a priest from Mannheim in south-western Germany, Father Lukas Glocker, said the tax was used to do essential good works.
"With kindergarten, with homes for elderly or unemployed, we've got really good things so I know we need the tax to help the German country to do good things."
While the decree severely limits active participation in the German Catholic Church, it does hold out some hope for anyone considering a return to the fold.
Until now, any German Catholic who stopped payment faced eventual excommunication. Although the measures laid out in the decree are similar to excommunication from the church, German observers say the word is carefully avoided in the decree.