Separation of church and state (secularism)
The objection to concordats is that they weaken the separation of church and state. This separation of two powerful institutions is a pre-condition for the free exercise of human rights. It is true that such separation does not guarantee human rights — as is shown by Communist dictatorships. But it has been proven again and again that lack of separation can threaten human rights — as is shown by societies living under religious rules, whether Sharia, Hindu Law, Halaka or Canon Law.
The history has a very important economic aspect. One of the dangers of subsidising religious institutions and granting them financial privileges (such as exemption from income tax, land and municipal rates, sales and other taxes) is that such institutions tend to become extremely wealthy, to aggrandize and to become states within a state. The corrective has often been a more or less violent seizure of the assets of the religious institutions, sometimes by the existing sovereign (as did Henry VIII), sometimes by revolutionary movements, which in many countries have had as one of their main objects the suppression of religious institutions and the seizure of their wealth. (Dissenting opinion, Victoria v. the Commonwealth, 1981, 33 ALR 321, at 358)
The desired separation of church and state can be legally acomplished in three ways: when a Supreme Court unpack a clause in the couintry's constitution, when the constitution itself spells it out, or through a simple "separation law".
♦ The 1791 First Amendment to the US Constitution, which explcitly forbids a state church, was later interpreted more broadly by the Supreme Court as also separating church and state. However, this legal evolution has not taken place in Australia. There a similar clause, s.116, in the 1900 Australian federal constitution is stil interpreted as merely preventing a state church.
♦ Other modern constitutions make it explicit that more is intended than the prevention of a state church. The 1948 constitution of India unpacks the meaning of "secular" in art. 15 and 25-28, and its Supreme Court in 1994 upheld these guarantees. The 1952 constitution of Communist Poland, (Art. 82.2), was less detailed, but its meaning was also clear. The 1961 constitution of Turkey explains "secular state" (Art. 2) through art. 24 and 25. And the 2013 constitution of Fiji explains the same phrase through art. 4 and 22.
♦ And, finally, church-state separation may be effected by legislation enacted by parliament, as in the French Separation Law of 1905.
However, constitutional separation is of little practical use where politicians do not dare to stand up to religious interests. An American doctor, writing about the recurring and needless measles epidemics, has said,
No lawmaker [...] dares to touch religious exemptions. It’s political dynamite. But with an estimated 30,000 children in the United States unvaccinated for religious reasons, that is a dangerous mistake.