Here is the current code (http://clerk.seattle.gov/~public/toc/table.htm):
Seattle Municipal Code
Title 15 - STREET AND SIDEWALK USE
Subtitle I Street Use Ordinance
Chapter 15.48 - Miscellaneous Acts
SMC 15.48.105 Conformance to applicable regulations for posting.
A. Handbills, signs and posters may be affixed to City-owned utility poles, lamp poles and traffic control devices under the control of the Seattle
Department of Transportation, except for freestanding stop signs and yield signs, and their posts, in accordance with the rules promulgated by the Director of the Seattle Department of Transportation pursuant to Chapter 3.02, the Seattle Administrative Code. Those rules shall regulate the time, place and manner of posting so as to advance the public purposes stated above so that (1) members of the public are afforded reasonable access to exercise their free speech rights, including being able to place signs at a height determined by the Director to be reasonable, consistent with other public purposes, which height shall not be greater than twelve (12) feet from the surface of the ground; and (2) handbills, signs, and posters affixed to any City-owned traffic control device, utility pole or lamp post will not unreasonably (a) contribute to a traffic hazard; (b) contribute to a safety hazard to anyone working on a utility pole, lamp pole or traffic control device; (c) contribute to a risk of fire; (d) contribute to visual blight; or (e) cause damage to City-owned property.
B. Pursuant to Seattle Municipal Code Chapter 23.55, handbills, signs and posters may also be affixed to City-owned poster boards and kiosks that are designated for handbills and signs.
C. A public agency may, with permission of the City, post traffic, parking and other regulatory signs on City-owned structures.
D. Other than as provided in this section, it is unlawful for anyone to affix any handbill, sign or poster upon a City-owned structure, or any
City-owned tree or shrubbery in any public place. City-owned structures include, but are not limited to, bridges and overpasses, monorail supports, retaining walls, fences, street furniture and shelters, and poles and posts not under the control of Seattle Transportation. Wires and appurtenances to any City-owned structure are also a City-owned structure.
there are three other sections (.110, .120 and .130) on removal which are too long to add here.
http://clerk.seattle.gov/~public/toc/15-48.htm
note: SMC 23.55 is the land use code for signs.
http://clerk.seattle.gov/~public/toc/23-55.htm