This is key to this-
1. The Second Amendment protects an individual right to possess a
firearm unconnected with service in a militia, and to use that arm for
traditionally lawful purposes, such as self-defense within the home.
That we can not just have them, but that we can use them. Using them requires ammunition.
To ban ammunition would infringe on my right to use my firearm.
It also specifically states that trigger locks/disassembly are an infringement. One could could also argue that laws requiring a gun to be locked away (such as I believe Cali has, correct me if I am wrong) are a similar infringement and that this ruling declares said law unconstitutional.