The plan launched this week, which the Home Office described as a one-year pilot, may involve adults who face deportation, impose a curfew on some or allow the detention and prosecution of those who do not comply with the new rules.

The British Home Office said the plan will test whether monitoring migrants with GPS devices will help “maintain regular contact” and “more effectively progress their claims,” as well as collect information on how many escape custody. But refugee advocates denounced it as treating desperate people seeking shelter as criminals.

The government indicated that among those who could be tagged would be people who challenged a decision to send them to Rwanda, after a legal showdown ended this week with the British government canceling the inaugural flight proposed under the heavily criticized policy.

Britain cancels flight to deport asylum seekers to Rwanda after court challenges

“The government will not be deterred as we plan for the next flight to Rwanda,” the Home Office said in an email.

“We will keep as many people in detention as the law allows but where a court orders that an individual due to be on Tuesday’s flight should be released, we will tag them where appropriate.”

While the government has said flying migrants to Rwanda would deter dangerous Channel crossings and stop smugglers, the policy has sparked uproar, including from human rights activists, the United Nations and the most senior bishop of the Church of England.

More than 10,000 people have entered Britain this year via the English Channel. In a single disaster in November, at least 27 migrants died while attempting the crossing.

Under the monitoring trial, people fitted with the location-tracking device will be required regularly to report in person to immigration centers or police stations.

Britain to fly asylum seekers to Rwanda to discourage illegal sea crossings

It was not immediately clear how many people could be tagged, although a Home Office report on the program published Wednesday said children and those who are 18 weeks or more pregnant would be exempt.

The instructions said that the potential harm to a person’s mental or physical health would be taken into account, as well as whether they were a victim of torture or modern slavery, but that this would not necessarily preclude the use of a tag. The program would target people who were released on immigration bail from holding centers after entering the country.

British Prime Minister Boris Johnson defended the plans Saturday as necessary to ensure “that asylum seeker can’t just vanish into the rest of the country,” according to British media, as critics highlighted fears about the impact on mental health and privacy rights.

Immigration lawyers and advocates have raised similar concerns about the use of electronic tagging devices on migrants in the United States.

The head of the Refugee Council charity, which is based in Britain, described the tagging program as a “draconian and punitive approach” against vulnerable people. Enver Solomon also disputed assertions that it would discourage refugees from undertaking the journey, calling instead for solutions that provide safe routes into the country.

“It’s appalling that this government is intent on treating men, women and children who have fled war, bloodshed and persecution as criminals,” he said in an email to The Washington Post.

Monish Bhatia, a lecturer in Criminology at Birkbeck, University of London, warned that monitoring migrants with the devices could lead to “anxiety, depression, suicide ideation.”

He noted it was unclear how long people would have to wear the tag and whether there are any privacy safeguards for the data the government could collect through the program. “Tagging is highly intrusive & experienced as punishment,” he tweeted.