I've racked my pea-sized brain over this and the only logical reason to make this a violation would relate to the dog being off leash and potentially out of control - a nuisance - potentially a threat to other dogs & the other public using the space.
Understandable to a point...I've seen some interesting dogs (and public) when they get off leash...
That said...the comment about feces & shellfish would've received a good chuckle....
Everyone & everything poops...
Oh ya...watched 3 awesome labs & their owner having a great time in the water at LP beach yesterday... Those dogs better get a job to pay that ticket...
If other locations in the Puget Sound allow it, then would it seem conceptually prudent to designate a specific area in LP that would be ok? How about the far end near the alley way to Lowman? Is this a Parks Dept. decision or City of Seattle?