The reason you aren't allowed to have dogs on Katahdin is because that type of animal doesn't actually go up into the alpine zone of Katahdin. The plants there

The reason you aren't allowed to have dogs on Katahdin is because that type of animal doesn't actually go up into the alpine zone of Katahdin. The plants there are extremely sensitive and cannot survive being stepped on by animals. And they are only able to grow for a couple weeks a year, so one dog can kill decades of growth by stepping on a small plant. So, I agree with the woods part, bring all the dogs you want onto the trail when you're in the woods, but when the rangers in Baxter State Park complain about people bringing dogs up the mountain, they are absolutely in the right.