Who has authority re: rules around STR?

[Mary Flynn Maes]

My husband and I have a STR in a rural part of Wisconsin (we live in CA, but I'm from the area and my whole family lives there). The property is located on a lake with a Lake Association that does not want us to be operating a STR. This was not disclosed when we bought the property, the previous owners basically told us the association had zero authority in the matter, and we never signed anything with the lake association agreeing to not use the property as we choose.

The lake association threatened to sue us for the vacation rental, and so we backed off on hosting. 

From what we can tell, the lake association is not like a homeowners association, so I am wondering what authority they have to tell us what we can do with our property? 

To broaden that a bit, the property is located in a township, which does have regulations around owning and operating a STR. We've looked into the regulations the township has established, and now, frankly, i'm wondering what authority the township has over our property. Some of the rules seem a little unrealistic (like requiring we have ADA-compliant ramps...in a lake house...) but more troubling is that the township requires STR owners to submit an application that the board must approve, and then that must be renewed/reviewed/approved annually. Ok, that's fine, I guess, until i realized that when looking at the membership of the township board - two of them are also members of our lake association! So... no, i don't see that application getting approved.

While a friend who lives in the area made the point that 'sure, they can make rules, but they can't enforce them,' (something about there not being a judicial branch of the township?) we're trying to be better humans than operating this under the radar and ticking off all our neighbors, not to mention potentially opening ourselves up to lawsuits or hefty fines.  But then again, I really don't like other people telling me what I can do with my property if they don't have the right to do so. 

Who has the authority to make and enforce STR rules in this situation (lake association? township? the county?) and how do we find out for certain? Is this under the purview of a real estate lawyer? Does anyone have experience with this situation or recommend a lawyer with experience in this situation?