Self-ID, in the jurisdictions in which it applies, is a legal process in which one makes a truthful declaration and is subject to legal governance like other similar declarations. There are legal sanctions for making a false declaration
However, in the UK there is no legal self-id for sex. So any man who wants access to things reserved for women because they are structurally oppressed and discriminated against cannot simply say he's a woman.
Most people don't realise that 80% of men who say they're women don't have genital reassignment surgery (GRS). And that includes men who have legally changed their gender (not their sex) through the attainment of of a Gender Reassignment Certificate (GRC) which sets up the legal fiction that they are women, in certain circumstances (bit importantly not all).
As a friend of mine said, "If they want us to accept them as women, they at least need to make the commitment to have their bollocks cut off."
I am opposed to self-identification for the simple reason that it fundamentally changes the basic definition of what it is to be female without asking women. There has been virtually NO consultation with women, no consideration of women's interests in the push in the UK for self-id, and the bullying of women who raise questions about the negative impact on women as a sex class (overall category) and as individuals, of self-identification as women by men. Women who've raised reasonable questions about the impact of self-id on women have been disciplined at work, lost jobs, been silenced and censored, and verbally & physically attacked.
So thanks for gthe most anti-woman post today, Booboostwo