DARWIN, Australia — Alison Richards, a 38-year-old graphic designer, had been living in Britain for five years when she decided to move home to Australia. Then she got sick with Covid-19 and lost her job.

“It was an awful experience,” said Ms. Richards, who spent six weeks without leaving her apartment, except for the night she became so ill she called an ambulance. “I thought, I’ll just pull myself through this and get home.”

She’s still waiting.

Ms. Richards is among tens of thousands of Australians stranded abroad because of government coronavirus restrictions that cap the number of people allowed on flights into the country. In mid-June, Ms. Richards booked a ticket to Sydney, but she has been bumped twice from her flight as a result of the caps.

Australia is one of the few places in the world that is barring citizens from leaving their own country and limiting the number of those who can return. The tough regulations have raised legal concerns about the right to freedom of movement, and have been especially painful for the large numbers of Australians who turn to travel as a balm against the tyranny of distance from the rest of the world.

“We wanted to take our kids out of the Australian bubble,” Daniel Tusia, 40, said of his family’s decision to travel internationally for a year. Mr. Tusia ended up spending $14,000 on business-class tickets to get his wife and their two children, one of whom has special needs, back to Australia after weeks of trying to get home.

“It never entered our mind before this point that Australia would actually physically and legally obstruct you from entering,” he said.

Scott Morrison, Australia’s prime minister, has framed the country’s hard-line approach as crucial to avoiding the kind of rampant spread of the virus experienced in countries that have travel restrictions that are looser or nonexistent, as in the United States.

“As an island continent, control of our borders has been a means by which we have kept Australians safe,” he wrote in a letter in August sent to those requesting consular assistance to return. He acknowledged that the measures were “frustrating,” but said they were necessary.

Last week, under growing pressure, Mr. Morrison said the caps on passengers entering the country would be raised to 6,000 per week from 4,000. Those numbers, though, depend on cooperation from the states and their capacity to quarantine arrivals, and travel industry experts said they still fell far short of demand.

They encouraged Mr. Morrison to pursue alternatives like allowing people traveling from countries with low infection rates to self-isolate, instead of mandating quarantine in government-designated facilities. Similar programs have been successful in Hong Kong, Singapore and Qatar.

While the authorities estimate that there are more than 35,000 citizens who want to return home, the airline industry says that based on booking statistics, as well as figures from the Australian Bureau of Statistics, the number is most likely closer to 100,000.

In the first week of September, more than 140 international flights with about 30,000 seats arrived in Australia, but only about 4,000 were filled. Often, business- and first-class seats are prioritized, meaning that only some can afford to come home.

Mohammad Khan, who has been stuck in Pakistan with his wife since March, said he was forced to buy business-class tickets after four of his economy tickets were canceled.

The couple could not afford the flights, but needed to return to Australia by December to ensure that Mr. Khan’s wife did not violate her visa requirements. So they sold their car in Australia. “We are in a miserable condition here, running out of money and time,” he said by email.

Emily Costello, 27, who began a job teaching English in South Korea last September, said there are just two flights to Australia before her visa expires, and they are both booked up.

She said she could not afford to return in March, when the pandemic began to escalate and Australia urged its citizens to come home. She has since finished her contract and has been couch surfing with a colleague while petitioning the Australian government for answers.

“I never in a million years thought I would be helping Australians to leave the country,” said Sonia Campanaro, a Melbourne immigration lawyer.

For those still stuck overseas, repatriation might be up to six months away. Some say they are considering a class-action suit against the federal government. Others have launched petitions and campaigns, including one through Amnesty International that asserts that leaving people stranded overseas is a breach of their human rights.

While it is true that international conventions ensure the right of people to return to their countries, the Australian government is not technically barring citizens from returning home, even if the airline caps are having that effect, law experts said.

Anyone bringing legal action against the government for stranding them would have to prove that the reasons for doing so were unjustified, they added.

For Ms. Richards, the graphic designer, her frustration at not being repatriated, especially when she followed government guidelines to remain in Britain until her illness passed, is building.

“I’m really, really angry,” she said. “All those people who say, ‘Oh, you should have come home sooner,’ I say, ‘Oh, would you have liked me to come home and infected an entire planeload of people?”

While contending with long-term complications of Covid-19, including heart palpitations and brain fog, Ms. Richards has written to numerous politicians pleading for assistance. She is currently booked on a flight out of London on Sunday, but is doubtful that it will go ahead, given the previous cancellations.

“It’s still confirmed, but I keep checking it every hour of every day,” Ms. Richards said. “Hopefully, I’ll be flying.”