Photos of Sydney men Mohamed Elomar and Khalid Sharrouf show the pair in violent poses, including one in which Mr Elomar is holding severed heads.
Senator Brandis says the pair have breached Australian law by fighting with terrorist group Islamic State, formerly known as ISIS or ISIL.
“They’ve certainly, from what we’ve seen on social media posts, committed other crimes as well,” Senator Brandis says.
“They may have committed war crimes.”
But lawyer for the Elomar family, Zali Burrows, has told Channel Seven that she believes the photos were doctored.
Ms Burrows thinks the duo are scapegoats who are being used to justify the strengthening of anti-terror laws.
The ramped-up laws, which include greater powers for security agencies, have bipartisan support.
They will be introduced after the parliamentary winter break.
