If they provide convincing argument for lawful impediment they could yet prevent the civil ceremony due at Windsor's Guildhall on April 8, says The Daily Mail.
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The legal complaints or caveats were delivered to the Superintendent Registrar for Cirencester Penny Fulford, who covers the Prince's Gloucestershire home Highgrove.
He, however, refused to discuss details of the complaints. But the existence of the objections was confirmed by Diane Waddington, registrar for Chippenham in Wiltshire, where Parker-Bowles has given notice of her intention to marry.
"I can confirm that at least three objections have been received by the Cirencester office and I have been copied the one lodged by Williamson," she said. In his complaint, Rev Paul Williamson described the marriage as "gross and offensive".
According to the law, once notice of a civil marriage has been posted, an objection can be lodged in writing or in person with the registrar at any time until the moment the couple become man and wife.
Objections must be made on legal grounds and the belief that "the marriage compromises the fundamental principles of English marriage law." Each objection has to be considered on its own merit and advice taken, if necessary, from the Registrar General of England and Wales, Len Cook, and his legal team.
It will be up to the local register office, however, to tell the couple whether their wedding can go ahead.
The Prince and his advisers are also said to have been warned of another possible challenge to next month's ceremony.
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Six senior lawyers - all of them staunchly traditional in their views - are said to be planning to lodge their opposition and might even be prepared to go to court over the issue, The Daily Mail claimed.
Legal experts have already cast doubt on claims by Lord Falconer, the Lord Chancellor, that laws banning members of the Royal Family from marrying outside the Church have been overturned by the Human Rights Act. Several have gone so far as to suggest that unless new legislation is swiftly brought in confirming the position, the marriage could be deemed illegal.
According to the report, the government is understood to be drawing up plans for an emergency legislation to wipe out any legal obstacles. But ministers would apparently be reluctant to push it through for fear of being associated with the wedding so close to a general election, it added.
