But the Australian Lawyers Alliance said the policy, which means new arrivals from those countries cannot apply for asylum for between three and six months, could breach the law by discriminating against Afghans and Sri Lankans.
"The law in Australia and the rule of law is such that laws have to be applied equally, irrespective of where a person comes from or their race," the alliance's Greg Barns told ABC Radio.
The government has said the changes have been introduced because of the improving and evolving situations in Afghanistan and Sri Lanka, and comply with Australia's international obligations to refugees.
But the country's rights body, the Human Rights Commission, said there was a risk the policy would discriminate against people based on their nationality.
"The Australian Human Rights Commission is fearful that it will lead to breaches of Australia's international human rights obligation, in particular our obligation under the refugees convention not to treat groups of people differently based on their country of origin," president Cathy Branson said.
Richard Towle, UNHCR Regional Representative for Australia, New Zealand and the Pacific, said his organisation would closely monitor the impact of the policy change on asylum-seekers.
"UNHCR believes that all asylum-seekers and refugees should be treated humanely and given the opportunity to have any claims for protection fairly assessed," he said in a statement late Friday.
"We are currently examining Australia's announcement, particularly with regard to issues around the detention of vulnerable persons and the provision of social support for those asylum-seekers subject to this suspension."
More than 1,800 boat people have arrived in Australia since the beginning of the year, the majority from Sri Lanka and Afghanistan -- countries which have endured years of conflict.