Arrested, de-arrested, detained at Heathrow
Gone are the days when one was merely arrested and charged with committing a crime; law enforcement officials now have any number of mechanisms for detaining people. Four men arrested on Friday at Heathrow Airport were subsequently "de-arrested" and detained under the immigration act. It's not clear whether they have been charged with a crime.
Four men were held in west London on Friday directly under the flight path of Europe's busiest airport, Heathrow. They were originally arrested under the UK Terrorism Act 2000 but were later "de-arrested" and instead were being detained under the Immigration Act 1971 and were being referred in custody to the Immigration Service. [...] Two other men were arrested outside Heathrow on Thursday; one was released, and one was placed into the custody of the Immigration Service. - CNN, Six new airport arrests in Britain.