Polish Bishops set their own rules for leaving the Church (2008)
Poland does not have church tax and so the matter of whether or not one wishes to be counted as a Catholic is of little practical significance. However, for many Poles it is still of symbolic importance. Until the possibility of defecting was abolished in 2010, the bishops laid out strict rules for permitting the baptised to excommunicate themselves.
In 2006 Pope Benedict was obliged to explore a “concept [...] new to Canon Law”, namely, how to deal with all the people who want to leave the Church. He sent a note to the bishops emphasising that this was to be kept under Church control.  Two years later the Polish episcopate issued a 22-point document summarised here and translated in full here.
These Rules governing the formal act of defection from the Church (an act no longer recognised in Canon Law as of 9 April 2010) were issued by the Conference of Polish Bishops on 27 September 2008. Their regulations make church-leaving much more difficult for Poles than for their neighbours in Austria and Germany where, due to church tax, the state is an interested party.
♦ The bishops begin by reminding you that, according to the rules of the Catholic Church, if you've been baptised you are obliged to remain in the Church and obey its edicts for the rest of your life. (§1)
♦ To leave the Church is to commit the sin of apostasy, which “in the most drastic way contravenes the obligation to preserve communion with the Church”, a sin which “hurts” the Church and should be actively discouraged. (§3).
♦ It isn't enough to clearly state your wish to leave in writing: you must also have “an inner desire” to do so and, in practice, the priest is the sole judge as to whether you really mean it. This gives him an opening to challenge you. (§4)
♦ If you're under 18 you can’t leave the Church (even if your parents have given their permission or have left the Church themselves). (§5)
The Polish ombudsman has supported this by citing §25.3 of the Polish Constitution that “the relationship between state and church and other religious organizations are based on the principle of respect for their autonomy and mutual independence of each in its own sphere”. Here freedom of individual conscience appears not to count. The applicant, as a baptised Catholic, belongs in the “sphere” of the Church, which is to say, under Canon Law. 
♦ You must bring along two adult witnesses when you ask the priest to release you, and these should include a parent or godparent. (§5) In other words family and friends who were honoured with the task of ensuring the baby a good Catholic upbringing are now to be humiliated by having to act as witnesses for their charge’s defection.
♦ The decision has to be expressed in writing and you must reveal “personal details of the apostate and witnesses” and your “motivation”, information which gives the priest an opening to apply pressure to remain. It also requires a baptismal certificate which is hardly necessary for identification, but whose replacement, if it had been lost, would require a further round of supplication involving a “voluntary payment”. (§6)
♦ The Church doesn't accept letters or emails, nor the mediation of any state official or authority. Permission to leave must be granted by the priest in person. (§7)
♦ Ostensibly to give time “for reconsideration”, the parish priest obliges you to return. It’s up to the priest to determine how long you need, (and he can even say, as one did recently, “Come back in two years’ time”). (§8)
♦ The Polish Personal Data Protection Act does not apply. (§11) This is because as a baptised Catholic you belong forever to the “sphere” of the Catholic Church, as set down in the Polish Constitution.
♦ Excommunication can be officially announced during the Mass in your parish church. (§13)
♦ No written confirmation of apostasy will be given: the Church has sole control over this record, as well. (§15)
♦ The Polish Church doesn't recognise “apostasy” committed abroad, where this is simpler to do. The apostate has to begin again and follow the restrictive Polish procedure. (§16)
♦ Even after leaving the Church you are to be subjected to social pressure to rejoin. The Catholic community is urged to give witness to the faith (§21) and to “pray for [the apostate] to return”. (§22)
These Rules governing the formal act of defection from the Church have been fully translated for the first time into English.
1. Actus formalis defectionis ab Ecclesia catholica, 13 March 2006 http://www.vatican.va/roman_curia/pontifical_councils/intrptxt/documents/rc_pc_intrptxt_doc_20060313_actus-formalis_en.html
2. This is the case of Maciej Walczak mentioned in Magda Działoszyńska, “Owieczka odchodzi”, (“Lamb leaves”), Gazeta Wyborcza, 9 December 2009. http://wyborcza.pl/1,75480,7346683,Owieczka_odchodzi.html