Elg dealt with an Indian who had been born in Indian country and only later moved to a state. At that time, many of those Indians didn't regard themselves as being "within the country," and in a very real sense, they weren't. Until the 20th Century, the Government dealt with Indian tribes through treaties, not by legislation. All through the 19th Century, many Indian tribes were at war with the United States Government. Indians born in Indian country were not then regarded as citizens because they were, in a very real sense, hostile aliens.
The Court's awkward language was a reflection of the fact that the U.S. Government officially claimed the legal right to rule over the Indians, but was still in the process of achieving control de facto. Once that was accomplished, Indians became citizens.
It's Elk, not Elg. You're confusing this with a 20th century case and a Swedish woman.
At that time, many of those Indians didn't regard themselves as being "within the country," and in a very real sense, they weren't. Until the 20th Century, the Government dealt with Indian tribes through treaties, not by legislation.
The Wong Kim Ark case was in conflict because of a treaty with China and the 14th amendment, not because of legislation.