Seems fair enough to me.

From the BBC:

Australian citizens returning home from India could face up to five years in jail and fines after the government made the journey temporarily illegal.

The health ministry said the ruling had been made "based on the proportion of people in quarantine who have acquired a Covid-19 infection in India". Earlier this week, Australia banned all flights from India.

...in an emergency situation, the government can make something a criminal offence overnight. At the height of the pandemic last year, the government beefed up its Biosecurity Act to give the health minister near unconditional powers bypassing parliament.

That's why citizens now trying to flee a danger zone can face jail for trying to come home. A legal challenge to this two-week ban will take time and be costly - public outrage and pressure may be the only effective remedy.

As at a year ago, when there was no real expectation of developing vaccines, any government had to choose some balance between the following strategies:

1. Continue as normal, accept that the number of deaths in the next year might double (your chance of dying if you catch covid-19 is approximately equal to the chance of you dying in the next 12 months anyway, and we can assume that within a year, most people would have caught it), ameliorate this as much as possible by temporarily increasing NHS capacity, and hope to achieve 'herd immunity' within a year or so.

2. Shut down the borders and/or have strict quarantine rules for arrivals, and wait for it to all blow over.

3. Impose a lockdown of whatever severity is needed to minimise transmissions and wait for it to all blow over.

If you shut down the borders, then hopefully the internal lockdowns wouldn't need so strict, but Australia ended up having to do both, which has so far superficially worked. Absent a vaccine, this would never have worked long term, it is merely a delaying tactic.

(The UK's response was pretty dumb. Having chickened out of strategy 1 - politically it is OK to do something dumb of every other government is being just as dumb - we left the borders largely open and had to impose correspondingly stricter lockdowns. In terms of deaths-per-million, strain on NHS and economic damage, this was a worse strategy than Australia.)

The Australian government has now decided to close its borders even more tightly, which is fair enough, this is for the benefit of their own citizens and their 'reward' for observing domestic lockdown measures and not going abroad. Flying abroad is tantamount to ignoring the domestic lockdown measures and as a quid pro quo, you can't come back in (to protect those who observed them).

So the bleating about "citizens now trying to flee a danger zone" falls on deaf ears with me, I'm afraid. They went to India voluntarily, so clearly didn't perceive it to be a "danger zone" and if there were no ban on coming back, I'm sure that just as many would be going there today.

Is this racist because it is largely Australian citizens of Indian heritage who are affected? I don't think so. Hopefully, the Australian government would have done the same if a 'white' country had the same high incidence of new variants and infections. (There again, knowing the Australian government, they might not have been quite so draconian with returnees from such a 'white' country).