The Office of the Data Protection Authority (ODPA) have published Contact Tracing Guidance (applicable during Stage 2 of the Bailiwick’s 2021 Exit from Lockdown): https://www.odpa.gg/information-hub/covid-19-qa/contact-tracing-guidance/
See also: Covid Q&A: https://www.odpa.gg/information-hub/covid-19-qa/