What would have stopped the Maidan protesters from being labeled as separatist military forces if they were well-armed? You're drawing distinctions where there are none.

Where do you think the Confederate forces got their firearms from? They just suddenly popped into existence the moment they became "separatist military forces"? They were the people with rights to bear arms bringing up arms against their tyrannical government.

The Confederacy was made of states. Even before the Civil War, each of these had militias.

I'm sure Yanukovych would have labelled them a separatist military - but would the remaining institutions agree? We don't have to assume that the protestors bring weapons from the beginning - it could come only in response to Yanukovych committing to violence.