Guernsey's former medical officer of health has had his legal challenge to the island's coronavirus regulations dismissed.
Dr Stephen Bridgman, who is undergoing 14 days of self-isolation, argued it amounted to "arbitrary detention".
Director of Public Health Dr Nicola Brink said she was sympathetic, but the isolation rules were in place to protect the population as a whole.
Judge Catherine Fooks dismissed the legal challenge in the Royal Court.
No order to costs was made and a written judgement is due later.
Dr Bridgman travelled to the island from New Zealand via Singapore and London Heathrow, and used public transport to make his way through London to Gatwick.
He received two doses of the Pfizer vaccine in New Zealand and argued he had been discriminated against as his vaccination status is not recognised in Guernsey because it was administered outside the Common Travel Area (CTA).
Since 1 July anyone who has been fully vaccinated within the CTA - the UK, Ireland and the Crown Dependencies - and travelling to the island from the CTA has been able to do so without the need for a test or quarantine.
Dr Brink said the island was at a "critical moment" in dealing with coronavirus pointing to the Alderney outbreak as an example of what can happen from a "single source introduction" of the virus on a small island.
She said it was impossible to quantify the risk Dr Bridgman posed from his travel history, noting he travelled through four international airports mixing with people from all over the world potentially exposing him to variants of concern.
She added there was currently no international system of vaccine recognition in place.