For easy reference, there’s a wiki article about that ruling with links:
http://en.wikipedia.org/wiki/United_States_v._Wong_Kim_Ark
In the view of the minority, excessive reliance on birthplace as the principal determiner of citizenship would lead to an untenable state of affairs in which "...the children of foreigners, happening to be born to them while passing through the country, whether of royal parentage or not, or whether of the Mongolian, Malay or other race, were eligible to the presidency, while children of our citizens, born abroad, were not".
They were, however, outvoted, and it seems the misgivings of the dissenters have come true. Personally, I don't have a bit of problem with this result.