Is the D.A. a Republican? If so I would start by sending him a copy of the newly written platform for the Wisconsin GOP which supports Constitutional Carry. If he doesn't agree with that then he is not an honest Conservative Republican.
Other than that whether he is republican or democrat he is still sworn to uphold the constitutions of Wisconsin and the U.S.
As far as the park restrictions go, the cities and the counties all have more parks in total then the state does. The amount of acreage if added together would amount to more acreage than is used for the state parks, therefore creating a larger area of prohibition making city and county laws ordinances more stringent then the state law.
Not to mention that your right to self defense does not go away inside a city or county park.
Maybe your DA has not been watching the news lately to see the cougar and bear sighting through out the state not to mention the criminal element.
If your DA doesn't get on board then form a campaign against him and help his challenger win at election time. Maybe that will get his attention.
At this time I have not received any reply back from the Calumet County DA who claims to be a Republican.