What is the test for the doctrine of conquest and what is the legal test for conquest?

The Court in Johnson v. M’Intosh acknowledged how “extravagant the pretension of converting the discovery of an inhabited country into conquest may appear”, but nonetheless rationalized the consequences as follows: [I]f the principle has been asserted in the first instance, and afterwards sustained; if a country has been acquired and held under it; if the property of the great mass of the community originates in it, it becomes the law of the land and cannot be questioned.