United Kingdom - Passport & Nationality - British Citizenship by Double Descent (Romein UKM pre 1949)
Legislation was passed in 2002 to address the unfairness that those born before 1 January 1983 to British mothers could not acquire British Nationality. However, elements of gender discrimination still existed. A recent Supreme Court Judgement in the UK has made it clear that it is unlawful for the UK Government to impose a requirement from the past on new applicants for citizenship where it was not lawfully possible for that requirement to be met at the time.
That's the theory, anyway. In practical terms (though there are circumstances where these won't apply), this should benefit those in the following situation:
a) born in a foreign country (which includes the United States and most European countries);
b) born between 1 January 1949 and 31 December 1982;
c) your maternal grandfather (i.e. your mother's father) was not born in the UK or Northern Ireland.; AND
d) you have the Right of Abode through a UK-born grandparent.