As it relates to "disciplining" the active duty militia or in providing punishments for actual crimes committed while in possession of "arms". It says nothing about regulating private firearms ownership for non-criminal uses.
In fact, the entire case is that RKBA is an individual Right and that legal uses of firearms are protected from blatant infringement by localities like DC.
Even if found to be an individual right, Washington, DC may regulate their use -- for example, children under 6 may not keep and bear handguns. Or do you have a problem with a law like that because it infringes the right of the people to keep and bear arms?