1 ) social contract
You (generic random "you") know you are not allowed into SSS as you are not of that sex so you do not enter into the SSS.
If you are the type of person who will go in anyway the individual who is lawfully using the SSS can call the police.
And the police can record the incident and then opt charge you with an offence if they feel it is for the public good.
- The police
Oddly enough police men as a total sex group were not lobbying the police authority to have the right to strip search women or people they think may be women.
That was the TRAs who pushed for a policy change where TW to be able to opt out on the basis of sex (pre 2000 sh) without harming their career to being obliged to carry out the search role on the basis of gender.
So ...
At the moment under the current UK policing rules any male officer or female officer who says she is a man can do a full 'hold the transman down using as many "men" as they deem necessary to safely and forcefully remove clothing' search as part of arresting her.
So this is a good thing or should it be changed?
This policy is due to the police unlawfully writing policy based on gender feelings not sex.
If the police continue to ignore the EA any TM who is arrested can be treated a man/male.
Once the police change the policy and are given proper training they could be lawfully sacked and criminally charged with an assault and sued in a personal capacity.