The action is being brought against the policy first announced by former home secretary Priti Patel by asylum seekers, along with the Public and Commercial Services union and charities Care4Calais and Detention Action.
Ms Priti had the legal “power” to certify that a country is safe for someone seeking asylum without it needing to be on a list of nations approved by Parliament, Lord David Pannick QC, who is representing the Home Office, told the court.
He said that “in all cases” of asylum claims the home secretary should form her view “about the general safety of the country itself and must also … consider the safety of the individual given their particular circumstances”.
Mr Pannick claimed that under an international convention on the treatment of refugees, the “concept of penalties … does not cover the removal of an asylum seeker to a safe third country”.
He said the UK was under “no obligation” and had “no duty” to assess an asylum claim if it chose to send a person to a safe third country.
The home secretary’s legal team said its written arguments: “Relocation to a safe third country is not a criminal penalty and is not imposed as a punishment.”
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The UN Refugee Agency has previously told judges that the government’s Rwanda plan was “incompatible with UK’s fundamental obligations” and that the east African country “lacks irreducible minimum components of an accessible, reliable, fair and efficient asylum system”.
In written submissions, the legal team also argued that there was no risk of those who are not granted refugee status in Rwanda being removed to their country of origin.
“Rwanda does not conduct forcible removals to the countries of which these claimants are nationals,” they said.
“There is also a financial incentive for Rwanda to accept individuals as they receive a payment to support the costs of processing each asylum claim."
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The home secretary has provided a minimum of three years funding for each “relocated individual”, and five years support for anyone granted refugee status if they stay in Rwanda, lawyers said.
Assurances have been given that “relocated individuals” will be provided with “adequate accommodation”, food, free medical assistance, education, language and professional development training, and “integration programmes”, the Home Office legal team said.
“There is therefore no blanket policy applicable to all. The measure requires an individualised, case-specific approach.
“The scheme structure makes provision for access to legal advice at multiple stages."
In April, Ms Patel said the “world-first” agreement with Rwanda had been made in a bid to deter migrants from crossing the Channel by providing one-way tickets to some asylum seekers.
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Former attorney general Suella Braverman replaced Ms Patel in Prime Minister Liz Truss’s Cabinet this week.
The High Court was previously told that Rwanda is an “authoritarian state” that “tortures and murders those it considers to be its opponents”.
Raza Husain QC, representing some of those bringing the case against the government, said that “a presumption of safety must be sufficiently supported at the outset” in relation to the consideration of an asylum claim.
In written arguments, Mr Husain said the home secretary had acted “irrationally” in determining Rwanda was “in general a safe third country”, and that “neither the claimed economic benefit” of the policy, “nor its asserted efficacy as a deterrent, has any evidential foundation”.
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The hearing at the Royal Courts of Justice in London, before Mr Justice Swift and Lord Justice Lewis, began on Monday and is due to last five days, with a second hearing in a claim brought by the group Asylum Aid taking place in October.
Decisions on both sets of claims are expected to be given in writing at the same time.