The issue is intent and clarification. Justice Roberts is well aware of the original intent, current status, interpretation, however, clarification within context of the law has evolved into a grey area requiring further review and definition. I would not be surprised if in fact the court accepts an Amicus Curiae or Brief to finally put this issue to rest.
The Court can only respond to a legal challenge.
If Congress passed say a law saying that children born to illegal aliens are not U.S. citizens- the Supreme Court by itself could do nothing.
Someone would have to file suit against Congress on constitutional grounds for the Supreme Court to consider the matter.