Not for the first occasion in this government's lifetime is there a dispute over a piece of legal advice.
Paperwork on Royal weddings has a long history
The Attorney-General's assertion that the war against Iraq was lawful continues to divide experts in international law.
Similarly constitutional lawyers are at odds over the legality of the marriage in a civil ceremony of Prince Charles to Camilla Parker Bowles.
It is doubtful whether the Lord Chancellor's statement will end the disquiet.
It is clear and unequivocal that the 1836 Marriage Act, which introduced civil marriage to England and Wales, did not apply to the royal family.
But the Lord Chancellor, Lord Falconer, says the 1836 Act has been supplanted in its entirety by the Marriage Act, 1949 and the Registration Service Act, 1953.
One clause of the 1949 Act reads: "Nothing in this act shall affect any law or custom relating to the marriage of members of the royal family."
Some legal experts, such as the former Attorney-General, Sir Nicholas Lyell, have suggested this leaves the royals subject to historic laws requiring them to marry in church.
This was the basis of the advice given by the then Lord Chancellor, Lord Kilmuir, to Princess Margaret when she announced her plan to marry Group Captain Peter Townsend in the 1950s.
According to Lord Falconer, that view was "over-cautious". He says the crucial clause in the 1949 Act is "a saving not an exclusion".
In other words it preserves a number of ancient procedures relating to royal marriages but does not exclude the royals from marrying in a civil ceremony.
Nevertheless Dr Stephen Cretney, of All Souls, Oxford, believes no statute permits a royal marriage in a register office and is calling on the government to introduce a one-line bill to remove any doubts about the legality of the Prince of Wales's second wedding.
Lawyers and academics are at odds over the union's legality
Lord Norton of Louth, a politics professor, said : "If the government's case is not considered compelling, I think we may have to fall back on legislation to clarify the position."
Lord Falconer has also introduced a thought which has been absent from the debate so far.
He says the Human Rights Act 2000 lends weight to the legality of a civil marriage ceremony for the Prince and Mrs Parker Bowles.
It required legislation to be interpreted wherever possible in a way that is compatible with the right to marry (article 12) and with the right to enjoy that right without discrimination (article 14).
Nothing would be more remarkable if this unprecedented controversy was to be finally settled by reference to a piece of legislation which New Labour regards as its landmark achievement.