There was confusion this week over the fate of people from other EU countries living in the UK.

While Britain is still in the EU, those people – who number more than 3 million – have the legal right to live and work here under the bloc’s principle of “freedom of movement”, but the Leave vote in 2016 changed their prospects dramatically.

Some of those people are now worried about their future legal status, particularly if Britain leaves without a withdrawal agreement.

Theresa May’s government launched the EU Settlement Scheme, which allows EU nationals living here – as well as family members and some others – to apply for permission to stay after 31 December 2020 in the event of a no-deal exit.

Campaigners are concerned that EU migrants who fail to apply for whatever reason will lose their legal status overnight, and they say only a change in the law will truly guarantee the residency rights that EU citizens have now.

What happened this week?

Boris Johnson used his first Commons statement as Prime Minister to “repeat unequivocally our guarantee to the 3.2 million EU nationals now living and working among us”.

He added: “I thank them for their contribution to our society and for their patience, and I can assure them that, under this Government, they will have the absolute certainty for the right to live and remain.”

At least one prominent EU citizens’ rights activist, the Conservative backbencher Alberto Costa, appeared to think that these words meant the new administration was agreeing to his calls for a change in the law.

On Thursday morning, Mr Costa was giving television interviews to that effect. It emerged later that Mr Johnson’s “guarantee” actually stopped short of bringing in new legislation.

The Prime Minister’s official spokesman later briefed lobby journalists that Mr Johnson had not meant to imply new legislation had been passed.

He was quoted as saying: “You heard him talk about the settlement scheme there. We want people to be registered, and we’re making an unequivocal commitment to make sure their rights are protected.”

It’s clear that the new administration feels that the current settlement scheme is enough to protect EU nationals’ rights, and that we don’t need a change in primary legislation.

Why do campaigners want a change in the law?

Some campaigners want the government to introduce primary legislation to guarantee the immigration status of EU nationals.

This is what happened in 1971 when the Immigration Act gave “right of abode” to certain immigrants to the UK from the Commonwealth. The law meant those people’s legal status was guaranteed without any need for them to apply for new status.

A change in the law would avoid the problem of people who did not get settled status losing their residency rights and effectively becoming illegal immigrants after the deadline passed.

EU citizens in this position might face a tough legal fight to stay in the UK.

They would arguably be in an even worse situation than those descendants of the Windrush immigrants who have faced legal difficulties if unable to produce historic proof of their immigration status.

Primary legislation also gets more scrutiny from parliament and is harder for ministers to tinker with after it is passed.

Has Mr Johnson broken a promise here?

During the 2016 EU referendum campaign, Boris Johnson, Priti Patel and Michael Gove put their names to a statement that read: “There will be no change for EU citizens already lawfully resident in the UK. These EU citizens will automatically be granted indefinite leave to remain in the UK and will be treated no less favourably than they are at present.”

Arguably, the settled status scheme fails to fulfil most of this, as EU citizens won’t “automatically” get leave to remain in Britain. They will only get it if they make an application to the scheme. And people who don’t go through the settlement process will clearly be treated less favourably than at present.

It could be argued that Mr Johnson, Ms Patel and Mr Gove were speaking as representatives of Vote Leave rather than the government at the time, so the promise they made then is not binding on the new administration. But of course, all three are now senior members of the new government.

Mr Johnson also gave an interview to the BBC in June this year in which he said: “One thing that would be right to do, and which I suggested straight after the referendum result three years ago, is take the provisions on citizenship, the offer that we make to the 3.2 million EU citizens in our country and do it in a supererogatory way, do it of our own accord, pass it through parliament.”

Campaigners say the words “pass it through parliament” mean this was a promise to introduce new legislation on the citizenship status of EU nationals.

If that reading is correct, Mr Johnson failed to keep that promise this week, although he did not spell out exactly what he meant by “pass it through parliament”.