The Australian Catholic Social Justice Council Chairman, who is also the bishop for Broome, says that there are questions over the legality of the military commission.
He says Mr Hicks, who is now expected to be returned to Australia to serve any remaining term of his anticipated prison sentence, has already been detained for more than five years including long periods in solitary confinement.
"Only one charge has now been brought against Mr Hicks, and there are grave concerns as to its legality and that of the military commission process. The length and severity of his detention, and his dignity as a human being, make it imperative to end his detention now," he said.
Speaking after a meeting of the Council, Bishop Saunders pointed out that the tribunal process has been condemned by many authorities, including Australian and international academics, lawyers, legal societies and civil rights groups.
The US itself, and key allies, have refused to allow their citizens to be tried under these rules, he said.
"Australia and the United States have a proud record in supporting the highest legal principles, both within and outside their borders. It is essential that those principles continue to be observed.
"Any legal process must be seen to dispense justice," Bishop Saunders said, in comments made before Hicks guilty plea became known.
In a surprise move, Mr Hicks yesterday pleaded guilty of having provided material support to al-Qaeda.
Mr Hicks, who has been held at Guantanamo Bay since late 2001, was the first inmate at the US military prison in Cuba to plead guilty to a terrorism charge.
Commenting on the plea, his father Terry said his son's admission was his only way out of "absolute hell" at Guantanamo Bay.
"It's the only way it looks like he's going to get out. No one's going to help him, the Australian government couldn't care, they don't care," he said.
The military commission is expected to sentence Mr Hicks this week.
Release David Hicks now, Bishop says (Australian Catholic Social Justice Council, Media Release, 27/3/07)
Guilty plea to get out: Hicks dad (Sydney Morning Herald, 27/3/07)
LINKS (not necessarily endorsed by Church Resources)
Australian Catholic Bishops Conference
David Hicks (Wikipedia)
Drop all charges against Hicks: bishop says (CathNews, 25/1/07)
Try Hicks or bring him home, Bishops tell Govt (CathNews, 4/12/06)
Cardinal Pell calls for fair trial for David Hicks (CathNews, 10/10/06)
Time for Hicks to go home, says Bishop (CathNews 23/8/06)
Bishop says Govt must ensure justice for Hicks (CathNews 22/9/05)
Hicks and Habib focus of bishop's Human Rights Day message (CathNews 10/12/04)
Council urges Govt to insist on human rights at Guantanamo Bay (CathNews 10/12/03)
Bishop says Govt can do more for Hicks and Habib (CathNews 13/11/03)
Press Council backs church official on unfair "traitor" headline (CathNews 14/11/03)
28 Mar 2007