David McBride sought leave from the High Court to appeal his imprisonment after he pleaded guilty to obtaining and disseminating classified defence information.
He was sentenced to a total of five years and eight months behind bars, with a non-parole period of two years and three months, meaning he'll remain in prison until at least August 2026.
His appeal on the conviction and the severity of the sentence was previously rejected by the ACT Court of Appeal.
The High Court's refusal to hear his case marks the end of the line for the former military lawyer.
McBride had argued his Australian Defence Force oath meant he had a duty to serve the Australian people and leaking the documents was in the public interest, which superseded his obligation to adhere to military's law.
But ACT Supreme Court justice David Mossop rejected this argument and said there was a need to deter similar actions when sentencing him
McBride took 235 documents, 207 of which were classified as secret, and shared them with journalists, leading to a series of reports that uncovered allegations Australian soldiers committed war crimes in Afghanistan.
A subsequent inquiry found credible information about 23 incidents of potential war crimes, which involved the killing of 39 Afghans between 2005 and 2016.
Human rights advocates have called for the Commonwealth to drop the prosecution and for McBride to be freed, saying his imprisonment will deter whistleblowing.
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