Symbolic Speech: The O'Brien Test

Once we are dealing with symbolic acts, O’Brien gives us a four-part test for determining when a government interest in regulating the nonspeech element sufficiently justifies the regulation of expressive conduct:

The government regulation of expressive conduct is valid if:

1) it is within the Constitutional power of government [raising an army]

2) furthers an important or substantial interest [preventing harm to the smooth and efficient functioning of the Selective Service System]

3) if the governmental interest is unrelated to the suppression of free expression; and

4) if the incidental restriction on free expression is no greater than is essential to the furtherance of that interest.

By the way, notice how the Court totally rejects a "purpose" test under the Free Speech Clause. The Court's objections here (p.1510) are basically the same as Justice Scalia's objections to a "purpose" test under the Establishment Clause. Notice that, somehow, the EC seems to be an exception to every normal rule the Court applies to every other constitutional claim--standing, incorporation, purpose, government speech, etc. Where in the text of the Constitution is this special status for the EC?