After the Supreme Court ruled that the scheme was unlawful, the government introduced a bill to make clear in UK law that Rwanda is a safe country.
The legislation – which was finally approved after intense political wrangling – orders the courts to ignore key sections of the Human Rights Act.
It also compels the courts to disregard other British laws or international rules – such as the international Refugee Convention – which would block deportations to Rwanda.
The UK government also signed a new migration treaty with Rwanda, which Home Secretary James Cleverly said guarantees that anyone sent there would not risk being returned to their home country.
The Rwanda Bill was fiercely criticised by opposition parties and by many charities representing asylum seekers.
After the bill passed, Illegal Migration Minister Michael Tomlinson said further legal challenges were expected.
Mr Sunak said that 25 courtrooms and 150 judges were available to deal with any legal cases, and there were “500 highly trained individuals ready to escort illegal migrants all the way to Rwanda”, with a further 300 awaiting training.
The FDA union, which represents senior civil servants, said it was launching a legal challenge because it feared officials implementing it could be forced to break the law.
In court documents related to its claim, government lawyers confirmed the earliest date for a flight would be 1 July – the first time a specific date has been mentioned.
The Asylum Aid charity has also told the Home Office it intends to take the government to court over the plan because the rulebook for officials now implementing the scheme undermines a key safeguard for refugees.
Separately, Northern Ireland’s Hight Court has ruled large parts of the UK government’s Illegal Migration Act should not apply in Northern Ireland because they breach human-rights laws and the Windsor Framework – the post-Brexit deal agreed between the UK and European Union in 2023.
The ruling could undermine the government’s plan to send some asylum seekers to Rwanda.