Two Australian residents suspected of travelling to the Middle East to assist in the battle against Islamic State have not been charged with any offences weeks after returning to Australia.

Tough new laws passed by Parliament last year, which include life sentences for those who participate in hostile activities overseas, were drafted to apply equally to those on all sides of foreign conflicts.

Matthew Gardiner reportedly travelled overseas to help Kurdish forces fight IS militants Credit:ABC

Prime Minister Tony Abbott has said that anyone who returns to Australia after becoming a foreign fighter will be arrested and charged, after reports emerged that three Australians who joined IS in Syria or Iraq are in talks with the government about potentially returning home.

"A crime is a crime is a crime," Mr Abbott said.