The European Convention on Human Rights has played a major role in the legal recognition of gender reassignment and also it has strongly influenced government to bring forward legislation for both civil partnerships and same sex marriage. Here is a brief history.
In Bellinger v Bellinger  UKHL 21
, the issue (in simple terms) was whether the law would recognise gender reassignment. More specifically, was Mrs Elizabeth Bellinger,
to Mr Michael Bellinger since marriage was (at the time) confined
to persons of opposite sex.
The leading speech was that of Lord Nicholls of Birkenhead which is a
masterful analysis of the development of the law. His Lordship noted
that the issue had been before the European Court of Human Rights (E Ct HR) on several occasions - Rees v United
Kingdom (1986) 9 EHRR 56, Cossey v United Kingdom (1990) 13
EHRR 622, and Sheffield and Horsham v United Kingdom (1998) 27
EHRR 163 - culminating in Goodwin v United Kingdom
(2002) 35 EHRR 18. In the earlier cases, the E Ct HR had permitted the UK a significant "margin of appreciation" in the making of domestic law. However, in Goodwin, the E Ct HR finally took
the view that the 'margin of appreciation' could no longer extend
to refusing to give legal recognition to gender reassignment and the UK was held to be in breach of Articles 8 (Respect for
Private and Family Life) and 12 (Right to marry).
In December 2002, the British government announced an intention to bring
forward legislation to allow transsexual people who can demonstrate
they have taken
decisive steps towards living fully and permanently in the
gender to marry in that gender. The eventual outcome was the Gender Recognition Act 2004.
The Bellinger case demonstrated the importance of looking at the
European Convention as a 'living instrument' rather than as a document
locked into the attitudes of the post-war world of the 1950s when the Convention originally came into force.
The 'living instrument' viewpoint, which is certainly not favoured by some
politicians, may be traced back to Tyrer v UK
1978 (corporal punishment in the Isle of Man). Of course, it is arguable that a change to our domestic law would have eventually arrived but it is impossible to say when it might have done so. The Convention was a valuable spur encouraging modernisation of the law. (For more on the living instrument approach see the article here).
The Bellinger case is also an important authority as to when the courts
will make a 'declaration of incompatibility' in relation to an Act of
Parliament. Such declarations became possible because of the Human Rights Act
1998 s.4 (HRA). Without the HRA, the legislation relating to marriage would not have been open to any form of challenge in our national courts. The declaration of incompatibility is a valuable mechanism written into the HRA and it enables the judges to record their view that legislation is not meeting the requirements of the European Convention. The declaration does NOT alter domestic law but it can lead to PARLIAMENT altering the law and the HRA contains a "remedial order" process to enable this to be done. However, the HRA does not impose an actual obligation on Ministers to bring forward amendment to the law.
Various transgender legal issues continue to arise. Some recent cases in the High Court are:
R (on the application of JK) v Registrar General for England and Wales  EWHC 990 (Admin),  All ER (D) 128 (Apr)
Carpenter v Secretary of State for Justice  EWHC 464 (Admin),  All ER (D) 08 (Mar)
and these are discussed at Halsbury's Law Exchange
Civil partnerships and same-sex marriage:
In 2004, in a separate development, Parliament enacted the Civil Partnership Act
permitting civil partnerships between same sex couples.
Article 12 of
the E Conv HR refers to 'men and women' having the right to marry
eachother and in Rees v UK (1987) 9 EHRR 56, the E Ct HR said that the
right to marry refers to the traditional marriage between persons of
opposite biological sex. It followed that there was no obligation on
States to recognise in law marriages or civil partnerships between
homosexuals - see Wilkinson v Kitzinger  EWHC 2022 paras 44-48.
To similar effect is Schalk and Kopf v Austria 2010. though here the court was cautious to note the contemporary
nature of its judgment in relation to Article 12 but held that, as matters stand, the question of
whether or not to allow same-sex marriage is left to regulation by the
national law of the Contracting State.' On this, see the interesting discussion by barrister Andrew Commins in Family Law Week.
The Civil Partnerships Act was clear recognition by Parliament of a
development across Europe to recognise in law the commitment made to
each other by persons of the opposite sex.
Furthermore, the Marriage (Same Sex Couples) Act 2013 has enable marriages to take place between those of the same sex.