As The Observer's editorial noted on Sunday, this is a specific anti-Catholic prohibition.
The prohibition on an heir marrying a Catholic, while remaining free to marry a Methodist, Muslim, atheist or Jedi Knight, is indefensible bigotry. (The separate condition that the monarch must be a member of the Church of England raises broader questions about the established church.)
Now The Telegraph reports that Deputy Prime Minister Nick Clegg has now been persuaded that this can't be changed.
Mr Clegg was initially attracted to the idea of repealing the Act but is said to have been persuaded that the difficulties raised by the Anglican Church were insurmountable.
It is odd that Clegg has thrown in the towel so easily on such a modest reform in the face of such weak and ill-founded objections. Remember that Clegg has promised to bring about the greatest constitutional reforms since 1832 (which rather implausibly means outstripping both the universal franchise and votes for women, not just devolution and freedom of information). Clegg demonstrates that he is more constitutionally conservative on this issue than John Selwyn Gummer, the former Tory cabinet minster who was an active member of the Church of England Synod before converting to Catholicism, and who sponsored private legislation to challenge this prohibition on Catholics.
Gummer described it as an "outrage" - but Clegg is reported to now understand and accept the obstacles to changing it. He spoke at ippr last Thursday of his self-image of being an insurgent crusader against vested interests, suffering a backlash for that reason. There is no evidence of that here.
The Church of England's reasoning conflates two issues - the religion of a Monarch, and of their spouse - in order to claim that treating Catholic spouses similarly to those of any other faith threatenss the Establishment of the Church.
The Church told the Telegraph this:
The prohibition on those in the line of succession marrying Roman Catholics derives from an earlier age and inevitably looks anomalous, not least when there is no prohibition on marriage to those of other faiths or none.
“But if the prohibition were removed the difficulty would still remain that establishment requires the monarch to join in communion with the Church of England as its Supreme Governor and that is not something that a Roman Catholic would be able to do consistently with the current rules of that church.”
The conflation depends on believing that Catholics always get the children.
The argument is still an illogical objection to the reform which is being proposed - that the prohibition on marrying a Catholic should go, without changing the separate requirement for the Monarch to themselves be a member of the Established Church.