A hearing into the powers of the ACT Firearms Registry has been told government contractors "probably" used illegally modified weapons during recent kangaroo culls in Canberra. The acknowledgement came during the ACT Civil and Administrative Tribunal (ACAT) appeal of Canberra-based gun manufacturer Gareth Crook, who was blocked from building sniper rifle prototypes for interstate police. Mr Crook's company was approached to design, test and potentially supply the high-powered rifles for use by special operations groups in 2015. However, in January the ACT Firearms Registry rejected the company's request to fit the rifles with suppressors and collapsing stocks, both of which were required by the brief but are illegal in the ACT. During Mr Crook's appeal he argued that contractors engaged by the ACT Government during recent kangaroo culls had been allowed to use suppressors on their weapons, and that he should be allowed to as well. The argument prompted the registrar's lawyer to acknowledge "no-one appreciated at the time ... that the use [of suppressors] may not have been, and was probably not, in accordance with the law." The lawyer noted the registrar had reviewed the legislation and planned to recommend changes to allow for the use of suppressors for "proper and legitimate purposes". ACAT President Geoffrey McCarthy said while he sympathised with Mr Crook's position, the ACT Firearms Registry was right to reject his application. However he noted that under the changes the registrar would push for, it was likely Mr Crook's application would be permissible. Push for legislative changes Mr Crook said he had been in touch with the office of Minister for Police and Emergency Services Simon Corbell, and was pushing for legislation changes to allow both himself, and kangaroo cull contractors to use suppressors. "You've obviously got to ... try these things and actually work out whether its an administrative decision process or whether it is actually a legislative issue," he said "As far as suppressors go, the Minister's already issued a regulation to that effect until legislation is potentially changed. "It actually does give an interim solution to both culling contractors and firearms dealers and manufacturers." The ACT Government has been contacted for comment.