The public forum doctrine was refined over the years, culminating in Perry Education Association v. Perry Local Educators' Association, 460 U.S. 37 (1983), where the Court established a three-tier categorization of public forums. The first category articulated in Perry was the traditional public forum. Traditional public forums include the streets, sidewalks, and parks discussed in Hague as being held in trust for the public. In a traditional public forum, the state may not restrict speech based on content unless it can show that its regulation is necessary to serve a compelling state interest and is narrowly tailored to achieve that interest.
Quote: An absolute prohibition on a particular type of expression will be upheld only if narrowly drawn to accomplish a compelling governmental interest. 
Quote: In U.S. Postal Service v. Greenburgh Civic Assns., 453 U.S. 114, 133, 101 S.Ct. 2676, 2687, 69 L.Ed.2d 517 (1981), we stated that "Congress . . . may not by its own ipse dixit destroy the "public forum" status of streets and parks which have historically been public forums.
. . ." [ibid]
We say: Nor may regulators.
Streets and parks have immemorially been held in trust for the use of the public and, time out of mind, have been used for purposes of assembly, communicating thoughts between citizens, and discussing public questions. Such use of the streets and public places has, from ancient times, been a part of the privileges, immunities, rights and liberties of citizens." Hague v. CIO, 307 U.S. at 515.
We note that the fourteenth amendment does not protect privileges and immunities from theft by Congress, or by regulators in the Executive branch, and we note that the clear meaning of the fourteenth amendment has long been ignored by the Supreme Court, yet we claim that neither Congress nor the Executive may infringe on this privilege to protest in the Center Zone, absent substantive due process.