On the Island it was AFAIK never illegal to enter into a Catholic marriage - however such marriages on Island were invalid in law thus any children would be illegitimate and if any partner died intestate their property would pass to the Lord (tho not sure if this was more theoretical than actual practice but I know of one relatively late case in which the Lord did not invoke this law) - if however the couple owned no property then the illegitimacy of children had little practical bearing - on the Island Catholics could own land etc and the penal laws of Ireland and England did not apply, the main problem was that out of the towns the couple could be presented for fornication + cohabitation but by late 18th century this applied less and less to the towns - the usual approach to avoid any problems was to marry in a CofE church and then hold the 'real' Catholic marriage service - there was a functioning church in Castletown from early 1820s and about the same period in Douglas but not always a resident priest - however until the large scale immigration of Irish from 1798 and then mainly thru the 1830s + 40s the numbers of Catholics was quite small. Things changed in 1849 - the reason for the calling in of copies of non CofE registers was to legitimise any children - Jews and Quakers had always been treated differently from late 17th C and their marriages etc accepted as valid under English law.