It is well settled that peaceful picketing on an issue of public concern in a public forum is constitutionally protected. Frisby v. Schultz, 487 U.S. 474, 479-81, 108 S. Ct. 2495, 2499-2500, 101 L. Ed. 2d 420 (1988). However, it need not be tolerated in all places and under all circumstances. Bakery & Pastry Drivers and Helpers Local 802 of International Brotherhood of Teamsters v. Wohl, 315 U.S. 769, 775, 62 S. Ct. 816, 819, 86 L. Ed. 1178 (1942). This is because picketing is not purely speech. 62 S. Ct. at 819-20. It also is inherently a form of conduct that may create substantial disorder or invade the rights of others in certain circumstances. See Tinker v. Des Moines Independent Community School Dist., 393 U.S. 503, 513, 89 S. Ct. 733, 740, 21 L. Ed. 2d 731 (1969). Such 'symbolic expression' or 'expressive conduct' may be validly regulated if the conduct itself may be regulated. Clark v. Community for Creative Non-Violence, 468 U.S. 288, 294, 104 S. Ct. 3065, 3069, 82 L. Ed. 2d 221 (1984); United States v. O'Brien, 391 U.S. 367, 376, 88 S. Ct. 1673, 1678, 20 L. Ed. 2d ...