Campaigners have asked the UK Ministry of Defence (MoD) to publish documents relating to the UK's 1980s arms deal with Saudi Arabia.
The £43m Al-Yamamah deal was the subject of a Serious Fraud Office (SFO) inquiry, following allegations BAE Systems paid bribes to members of the Saudi royal family to secure the deal.
The investigation, which was called off in 2006, is currently the subject of a High Court appeal, where anti-arms campaigners are seeking a ruling that will force the SFO to revisit the deal.
The Campaign Against the Arms Trade (CAAT) has made a Freedom of Information request for documents relating to the original deal.
The MoD refused access, citing confidentiality issues.
An Information Tribunal will rule whether the MoD was right to refuse the request.
The High Court has yet to rule on the SFO's decision to drop the 2006 investigation.
By Elizabeth Clifford-Marsh