In my neck of the woods, the neighboring town of Vancouver, WA passed some smoking laws about 10 years ago that prohibit all tobacco products in public parks. Mainly because cigarette smokers were leaving their butts everywhere instead of disposing of them properly. Not really anything to do with second-hand smoke, but just trying to keep the parks cleaner. Over the past 10 years I've not heard of anyone really enforcing the law as the local police have more important things to deal with than someone smoking a cigarette, cigar and/or pipe in a park.
In my town I have on many occasions taken a pipe or a cigar on a walk while out walking one of my dogs. Other times I'll take a pipe and visit the local lake and enjoy a walk on the trails or just sit and enjoy the view. No laws prohibiting smoking in our local parks. I've seen numerous people enjoying the seating in our downtown area with a cigarette, and never an issue.
If you're minding your own business and not generating complaints from other people, I highly doubt the local law enforcement will contact you about smoking a pipe while on a walk or sitting on a park bench etc. If they do, then they're really bored and will most likely just ask you to put it out.