United Kingdom - Passport & Nationality - British Citizenship (British Father Sec 4E-J)
In the past, British nationality could pass from mother to child in the case of an illegitimate birth (in other words, a child born to parents who were not married at the time of birth). In some circumstances, the birth could be legitimised if the parents subsequently got married.
To take into account modern trends and to reflect that it is becoming socially more accepted for children to be borne out of wedlock, new legislation became effective from April 2015 to allow British nationality to flow from a British father to an illegitimate child.
This means that where someone has been disadvantaged in the past due to being classified as an illegitimate child, it will be possible to lodge a remedial application to give the subject the rights that they would have had from the start but for this prior discrimination. The new law even allows some to qualify if they were disadvantaged as an illegitimate child with the relevant country's independence arrangements.
However, there are catches as always. We can deem some illegitimate children British by operation of law using the domicile laws of other countries. If someone is already a British Citizen by operation of law, it would be wholly inappropriate to register that person as a British Citizen because it would;
a) Potentially remove rights from any children already born to that person, or
b) Remove citizenship of another country because the subject has made a voluntary application to acquire citizenship.
It therefore follows that anyone who might have a valid claim under these new proposals should always consider the potential negative implications. For this reason, this route to British Nationality is considered a Non-Standard one.