Justice Brett Kavanaugh joined the group to form the 6-3 majority based on the grounds of 1950’s federal legislation rather than the Constitution . So IMO he still thinks that president trump didnt violate the 14th amendment plus he also gave republicans an option to pass a new legislation and amend federal laws to establish exception to birthright citizenship.
For congress to pass this legislation you need a vote of atleast 67 percent or more in both chambers which is next to impossibility.