The concurring opinion is controlling on the issue of regulations for leafleting.

It was a 4-4-1 decision. 4 judges found it was a nonpublic forum and that the Port Authority's ban on leafleting was constitutional. 4 judges found that it was a public forum and the ban was thus unconstitutional. Justice O'Connor agreed with the first four, finding that it was a nonpublic forum. But she agreed with the other 4 in finding that the restriction in place by the Port Authority was unconstitutional. Thus, there's a majority who find that an airport is a nonpublic forum and there can be restrictions on speech and there's also a majority who found that a total ban on leafleting is unconstitutional. Because O'Connor's concurrence is the decision that comports with both those holdings it is controlling.