The Federal Government will this week introduce legislation to ban refugees and asylum seekers on Manus Island and Nauru from ever coming to Australia.

The proposed changes have sparked a heated debate since being announced last week, but how do they differ from what's already in place?

What does the Government want to do?

The Government wants to change the Migration Act so that refugees and asylum seekers in offshore processing centres would never be allowed to come to Australia.

So even if a person was found to be a genuine refugee and gained citizenship in another country, they could not access any kind of visa — such as a business or tourists visa — to come to Australia in the future.

The legislation — which is not yet public — will include ministerial discretion, so the Immigration Minister could intervene in individual cases.

Who could it affect?

The legislation is designed to affect people who came to Australia by boat after mid-2013, a cohort which was sent to offshore processing centres on either Manus Island or Nauru.

It may also impact on people who are currently in Australia, if they had been transferred from an offshore centre for medical treatment.

The legislation won't affect people who were aged under 18 years at the time of their transfer offshore.

According to the latest statistics from the Department of Immigration and Border Protection, 1233 people remain in the offshore centres — 823 on Manus Island and 410 on Nauru.

How does this fit with international law?

The Coalition is adamant that the proposed changes are in keeping with Australia's international obligations.

Article 31 of the United Nations' 1951 Convention relating to the Status of Refugees states that signatories "shall not impose penalties, on account of their illegal entry or presence, on refugees".

It further states the advice should apply to refugees who come directly from a life-threatening region.

Are we taking any refugees?

Yes — the Government is continuing to process the 12,000 Syrian and Iraqi refugees to be taken in as part of a one-off agreement announced by the former Abbott government.

As of September, about 3,500 people had already been resettled.

Australia will also resettle refugees from Central America as part of its annual intake, set to remain at the 2018-19 level of 18,750.

Where would people on Manus and Nauru go?

If asylum seekers on Manus Island are found to be genuine refugees, they can resettle in Papua New Guinea.

For those on Nauru, they can resettle there or in Cambodia as part of the $50 million agreement struck with Australia.

Other than that, we don't know — the Coalition has stated it is in discussions with countries, but is yet to name any.

Last week, Foreign Minister Julie Bishop said the Government was working in particular with the 45 countries in the Bali process.

Not all the countries may be viable options and of the countries who are members of the Bali Process, 14 have ratified the Refugee Convention.

The US has not, but it does have similar obligations by ascending to the Protocol Relating to the Status of Refugees in 1968.