I dont understand why there should be a need for a law to ban outdoor wood boilers.
I personally own an outdoor wood boiler. If those who have one would learn to regulate what they burn and how much at one time, then there should be no problem with smoke.
On the other hand, if those that make the laws would use enforcement and place fines on those who do burn garbage or use their boilers as incinerators, those are the people that should be taken care of.
If I am speeding down the road recklessly and get caught. I know I will get a ticket and have to pay a fine (rightly so). But I dont see a law to ban all vehicles on the road, because of a few bad apples.