An officer on the side of the road cannot conduct a strip search under stop and search powers.
Where strip searches are allowed, the requirement for same sex officers is within PACE code of practice C, which is issued by the Secretary of State.
Neither of these bits of legislation are the 2010 EA, so it's unclear to me that the SC ruling should affect them, though the SC did highlight and put clear weight on the BLOODY OBVIOUS fact that single sex provision is provided because of biology, not feelz, and maybe it was that bucket of cold water that has jolted some forces into doing the right thing.
When conducting same sex activities under PACE (like strip searches), there is an entire annex (annex L) dedicated to deciding which sex to treat people as with a focus on transgender people. However, it only considers the sex of the detainee, not of the officer conducting the searches.
ANNEX L ESTABLISHING GENDER OF PERSONS FOR THE PURPOSE OF SEARCHING AND CERTAIN OTHER PROCEDURES
1. Certain provisions of this and other PACE Codes explicitly state that searches and other procedures may only be carried out by, or in the presence of, persons of the same sex as the person subject to the search or other procedure or require action to be taken or information to be given which depends on whether the detainee is treated as being male or female. See Note L1.
2. All such searches, procedures and requirements must be carried out with courtesy, consideration and respect for the person concerned. Police officers should show particular sensitivity when dealing with transgender individuals (including transsexual persons) and transvestite persons (see Notes L2, L3 and L4).
(a) Consideration
3. In law, the gender (and accordingly the sex) of an individual is their gender as registered at birth unless they have been issued with a Gender Recognition Certificate (GRC) under the Gender Recognition Act 2004 (GRA), in which case the person's gender is their acquired gender. This means that if the acquired gender is the male gender, the person’s sex becomes that of a man and, if it is the female gender, the person’s sex becomes that of a woman and they must be treated as their acquired gender.
4. When establishing whether the person concerned should be treated as being male or female for the purposes of these searches, procedures and requirements, the following approach which is designed to maintain their dignity, minimise embarrassment and secure their cooperation should be followed:
(a) The person must not be asked whether they have a GRC (see paragraph 8);
(b) If there is no doubt as to as to whether the person concerned should be treated as being male or female, they should be dealt with as being of that sex.
(c) If at any time (including during the search or carrying out the procedure or requirement) there is doubt as to whether the person should be treated, or continue to be treated, as being male or female:
(i) the person should be asked what gender they consider themselves to be. If they express a preference to be dealt with as a particular gender, they should be asked to indicate and confirm their preference by signing the custody record or, if a custody record has not been opened, the search record or the officer’s notebook. Subject to (ii) below, the person should be treated according to their preference except with regard to the requirements to provide that person with information concerning menstrual products and their personal needs relating to health, hygiene and welfare described in paragraph 3.20A (if aged under 18) and paragraphs 9.3A and 9.3B (if aged 18 or over). In these cases, a person whose confirmed preference is to be dealt with as being male should be asked in private whether they wish to speak in private with a member of the custody staff of a gender of their choosing about the provision of menstrual products and their personal needs, notwithstanding their confirmed preference (see Note L3A);
(ii) if there are grounds to doubt that the preference in (i) accurately reflects the person’s predominant lifestyle, for example, if they ask to be treated as a woman but documents and other information make it clear that they live predominantly as a man, or vice versa, they should be treated according to what appears to be their predominant lifestyle and not their stated preference;
(iii) If the person is unwilling to express a preference as in (i) above, efforts should be made to determine their predominant lifestyle and they should be treated as such. For example, if they appear to live predominantly as a woman, they should be treated as being female except with regard to the requirements to provide that person with information concerning menstrual products and their personal needs relating to health, hygiene and welfare described in paragraph 3.20A (if aged C Codes of practice – Code C Detention, treatment and questioning of persons by police officers 89 under 18) and paragraphs 9.3A and 9.3B (if aged 18 or over). In these cases, a person whose predominant lifestyle has been determined to be male should be asked in private whether they wish to speak in private with a member of the custody staff of a gender of their choosing about the provision of menstrual products and their personal needs, notwithstanding their determined predominant lifestyle (see Note L3A); or
(iv) if none of the above apply, the person should be dealt with according to what reasonably appears to have been their sex as registered at birth.
5. Once a decision has been made about which gender an individual is to be treated as, each officer responsible for the search, procedure or requirement should where possible be advised before the search or procedure starts of any doubts as to the person's gender and the person informed that the doubts have been disclosed. This is important so as to maintain the dignity of the person and any officers concerned. (b) Documentation
6. The person’s gender as established under paragraph 4(c)(i) to (iv) above must be recorded in the person’s custody record or, if a custody record has not been opened, on the search record or in the officer’s notebook.
7. Where the person elects which gender they consider themselves to be under paragraph 4(b)(i) but, following 4(b)(ii) is not treated in accordance with their preference, the reason must be recorded in the search record, in the officer’s notebook or, if applicable, in the person’s custody record.
(c) Disclosure of information
8. Section 22 of the GRA defines any information relating to a person’s application for a GRC or to a successful applicant’s gender before it became their acquired gender as ‘protected information’. Nothing in this Annex is to be read as authorising or permitting any police officer or any police staff who has acquired such information when acting in their official capacity to disclose that information to any other person in contravention of the GRA. Disclosure includes making a record of ‘protected information’ which is read by others.