Before we get to the “well regulated” clause you’re referring to, we need to understand “militia”.

First, I’ll direct your attention to Article I, Section 8, parts 12 and 13. These give Congress power to create armies and a navy.

Next we’ll go to part 15: Congress is not given power to create the militia. Congress’s power is to call forth the militia. The militia exists without having been created by Congress.

The militia consists of everyone that Congress can call forth. Who is that? Who can they call forth?

We know from 10 USC 246 that they have already provided for calling forth able bodied male citizens (and those intending to become citizens) aged 17 to 45, as well as members of the National Guard, regardless of age, sex, physical abilities, or citizenship status. They limited themselves to men, aged 17 to 45; they are free to revise that criteria any time they want. They are free to change the age range to 16 to 60. They are free to change “able bodied” to “sound mind”. They are free to include women. They are free to include non-citizens and foreign volunteers. Even children have been allowed to come forth when Congress has called in the past.

Everyone that Congress can call forth is the militia. The militia is the people. The same people to whom the right is guaranteed in the 2nd amendment.

“Well regulated” refers to Part 16, in which Congress is granted the authority to provide “discipline” (training standards), and the state is granted the authority to conduct that training. The second amendment explicitly limits Part 16 powers as they pertain to the right to keep and bear arms. Congress has the power to arm the people; they do not have the power to disarm the people.