Yes, the majority ruling leaves the premise extremely wide open, but the fact remains that there has not been a specific ruling on this (yet, although I feel it’s inevitable.)
However, there is certainly no denying the intent of the law.
There is also no reason why Congress couldn’t close this loophole nor is there any reason it would require “changing the Constitution”.
The evident intention, and the necessary effect, of the submission of this case to the decision of the court upon the facts agreed by the parties were to present for determination the single question stated at the beginning of this opinion, namely, whether a child born in the United States, of parent of Chinese descent, who, at the time of his birth, are subjects of the Emperor of China, but have a permanent domicil and residence in the United States, and are there carrying on business, and are not employed in any diplomatic or official capacity under the Emperor of China, becomes at the time of his birth a citizen of the United States. For the reasons above stated, this court is of opinion that the question must be answered in the affirmative.
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That doesn't sound "extremely wide open" to me. It's pretty cut and dry.