When Blackstone Rangers and Black Panther Party were armed and politically active, they weren't characterized as "militias".
What is a "well regulated militia"?
Things that are required for a group of armed people to be a "well regulated militia":
- a roster
- periodic musters
- a code of behavior--the US military has Uniform Code of Military Justice--including a system for disciplining those who violate the rules.
- a chain of command
- a unit of government that charters the militia & holds it accountable
A bunch of people with guns isn't a militia by any reasonable definition.
Congress should pass a law that defines militias and requires them to be recognized directly or indirectly by either a US state, territory or the federal government.
All states, District of Columbia and [inhabited] territories would be empowered to recognize a militia, empowered to conduct operations within the state, district or territory as defined by law.
But all militias need to demonstrate that they have a roster, periodic musters, a code of behavior and a chain of command. And there needs to be an elected official or elected body to which the militia answers.
Anything less is not a "well regulated militia" as defined by the Second Amendment.
By defining "well regulated militia" Congress would separate the people who are acting within the Constitution and those who are menacing the rest of society.