One Nation campaign signs backing Ben Roberts-Smith have reportedly appeared outside pre-poll booths in southern NSW ahead of Saturday's Farrer by-election, raising concerns from legal experts.The minor party's corflutes feature an image of the former soldier in military uniform, wearing a beret and winged badge of the Special Air Service (SAS), alongside the words: "He fought for us The signs have reportedly been seen at pre-poll booths in Albury, where material for One Nation candidate David Farley was displayed.One sign stated it was authorised by One Nation leader Pauline Hanson, who has sought to position herself as Roberts-Smith's most vocal political backer since he was released on bail last month.In a statement provided to the ABC, a One Nation spokesperson said it was the only political party publicly backing Roberts-Smith and wanted voters in Farrer to be aware of this