I have far from an encyclopedic knowledge of the ACLU and it's history, so I could be wrong. I had thought they have in the past done some 2nd amendment cases, and continue to do so. Their position is less strong, maximalist, whatever you want to call it than some other groups e.g. the NRA. They also don't see the need to focus a lot of resources on those types of cases when other groups do that, and effectively.