Peace activist Scott Parkin was classified a national security risk while on holiday in Australia last September and was deported.
Iraqi asylum seekers Mohammad Sagar and Muhammad Faisal, who have been detained for more than five years, also received adverse security assessments from ASIO.
The three men applied to the Federal Court for access to the ASIO documents after the federal government refused to release them.
Justice Ross Sundberg today granted them access to the assessments to prepare for a case that will challenge the ASIO decision deeming them security risks.
In his judgment, Justice Sundberg said he accepted the three men's argument that they needed access to the ASIO documents for their case to prove they were not national security risks.
Outside court, the men's lawyer, Anne Gooley, welcomed the decision.
"This is a really important step in this process to clear these men and for the two Iraqis to enable them to be resettled after five years of effective imprisonment," she said.
One of the men remains detained on Nauru, while the other was moved recently to a psychiatric facility in Brisbane.