If you believe that a policy is against the law, how do you go about bringing up the issue without sounding like a "Barracks Lawyer"?

There is a policy that states that I can not have a personal firearm while I am stationed in DC. I asked my CoC if I could store my firearm off of government property with a trusted friend, who was willing to do so. I was told that since I am on "Deployment" here in DC, that my command has more authority over this issue than a typical unit would at their home station. 

I have provided them with a law several months ago, and contacted a JAG who told me that I was correct in thinking that this policy was against the law. What do I do to show my CoC that they do not have the legal authority that they think they do? 

I have already submitted a request for exemption to policy, which was denied. I then provided my BN Commander with the law, and he said that he would have his JAG look into it. That was well over 2 months ago, and I haven't heard anything. 

As I am seriously considering trying to go to sniper school, I believe that it is important to shoot as often as possible. However, without access to my personal firearm I am severely hampered in that respect. 

I would like some advice for how to go about this issue in a way that will not be deemed as insubordinate. Especially since I have already been told, by my command, that I do not have the right to have a personal firearm in the DC area, regardless of where I store it. 

Thank you for your responses.