these must have seemed good ideas to some idiot
Laws are usually reactive rather than proactive, they're made because they are seen to be needed.
Maybe some kids got shot by the police because their squirt guns looked real. I'm vaguely aware that fake guns over your side of the pond need a bright red cap on the end of the barrel but I guess it wasn't always so.
Not sure about silly string. Maybe it's just too silly.
No more than two dogs seems sensible to me.