The SC ruling was useful in a very down-to-earth way: it re-asserted the established and accepted meaning of the words 'man' and 'woman'
the ordinary meaning of those plain and unambiguous words corresponds with the biological characteristics that make an individual a man or a woman.
There are often posts showing that some dictionaries, esp online ones, the Cambridge Online seems to be a fave, give not just the 'dictionary definitions' of words, but also their current usage in popular speech.
So 'sick' can mean 'good' as well as unhealthy, just as 'gear' meant good as well as...well all the things that gear can mean! - in popular speech in the 1960s.
These meanings are passing fads - what is the current status of 'dope', I wonder? does it still mean sick? or is it as hopelessly out of date as gear?
When laws were drafted using the words 'man' and 'woman', it is reasonable to say that they only meant established and accepted meaning, not the popular uses listed down the page a bit in the Cambridge Online Dictionary.
I know that laws can be updated as words change, for instance copyright law has had to keep up with new forms of recording/broadcasting technology
In Mandarim Records v Mechanical Copyright Protection Society (Ireland) Ltd,122 Barr J held that a Power CD which contained both sound recordings and other material including text and graphics, constituted a record within the meaning of the Copyright Act, 1963. He held that the fact that the framers of legislation would not have envisaged that the type of technology under consideration was not in itself a bar to the inclusion of the technology within an existing statutory framework. It was, he said, patently desirable that, where possible, advances in technology, even those which could not have been envisaged by the framers of an Act, should be accommodated in statutory interpretation by the courts. However, he held that this accommodation can be made only where the words of the provision were not strained beyond their ordinary meaning. Due regard must be paid to the structure and intent of the statute. [my emphasis]
Statutory Drafting and Interpretation : Plain Language and the Law
[Irish Law Reform Commission]
So 'advances in technology' may be accommodated in interpretation - but changing the 'ordinary meaning' of words is not acceptable, especially if it goes against the obvious intent of the law.
The UKSC came to the same conclusion about the meanings of 'sex' 'man', 'women', and although they only referred specifically to EA2010, the idea that a word can mean one thing in one law and the opposite in all others seems daft.