If Ukraine, as a sovereign nation, were to invite NATO onto their territory to help them with the uprising in the east, no laws would be broken, nobody invaded, then surely using all power available and with much haste, they could crush the rebels before the Russians had time to help defend them, and besides the rebels would have no legal grounds to invite the Russians to help them, seeing as the east is legally part of the Greater Ukraine, in fact the west should have moved quicker on The Crimea and crushed this precedent from happening, it's like the Nazi's all over again....