Yes, the fines are legally enforceable because (generally) you have to agree to them in order to purchase the house - joining the HOA and being bound by its rules either literally or functionally becomes a permanent part of the deed to the property. There isn't a legally viable argument that you only signed that part under duress because you could have chosen to live somewhere else instead. You could technically get a like-minded group of neighbors to run for the HOA leadership roles and eliminate the petty rules, but the rider contract to the deed still exists.