I'm sorry I did not see exactly what type of rifle you were talking about, but if your talking your standard hunting rifle Win, Rem, or whatever, a good secure case bolted to a safe location on the bike. or you can sling it on your back, if a AR style take it apart and put it in a backpack, or course you can sling it also, as you say there may be no legal issues but if you were to crash with a rifle slung on your back you could be hurt, like maybe getting stabbed by the rifle, which would be bad, it would tear you up worse than if you did not have the rifle on your back......... and you could cause damage to the rifle