ANSWER:
We say that non Muslims are kafir, those who prostrate to graves and seek refuge in peers and supplicate to them are Mushrik.
Those who legislate laws contradicting sharia law and make this a law to be followed and stating that this is better or equivalent to sharia law are apostates. We say that whoever does this particular sin is a kafir, only after the conditions are fulfilled and the obstacles are removed. This is done by judge and scholars and not by individuals.
On the other hand, one of the characteristic of Khawarij is that they give takfeer to specific individuals and to most those who go against them. They give takfeer to anyone who makes a major sin.