The problem can also lay in the interpretation of existing laws also.
The Cleveland Metro-parks system form a chain of green areas circling Metropolitan Cleveland, to such an extent that it is referred to as the Emerald Necklace. Over the years, the Metro-Parks have acquired certain properties and folded them into the system such that any large (acreage wise) area is almost exclusively under their jurisdiction. They are their own governmental entity with their own police force (not however judicial system, as at this time they must use local courts). All of this and.... you guessed it. Rocket launching is verboten.
They don't have a law, from what I understand from my conversation with some park rangers, specifically prohibiting model rocketry, but one which can be warped to include it. I think, and don't quote me on this, that the original law was created to make items like potato cannons illegal, since it states, going from memory on this. something along the lines as objects launched and or fired .....
I do plan on trying to overcome this ban one day, but at this time I have too many other projects on the line regarding trying to get my rocket company off the ground, and focusing on a smaller battle with a local councilman and a city owned park.
One additional tact I plan on utilizing is to possible have a law enacted which states that the parks can be used for model rocketry by MEMBERS OF A MODEL ROCKET ASSOCIATION WHOM ARE COVERED BY SOME SORT OF FINANCIAL RESPONSIBILITY. Letting the politicians know that we are concerned about our activities even to the point of being financially responsible for problems, takes an additional concern off their minds. It also leads to another positive point in your safety lecture by pointing out the low incident rate of model rocketry insurance claims. I believe the information is available through the NAR or I thought I saw it there once. I am sure it is available somewhere.
Not that I'm against HPR, I think it has it's place, but if I recall correctly, the most egregious of those claims I saw dealt with High Power. So, if not a problem, you can also consider a proviso that High Power Rocketry not be considered under certain circumstances. That would be your call and what your underlying goal is. It might be a tactic to even initially not have the high power and work into it at a later time. I am sure that rocketry got its foothold in the initial years by limiting the size and power of the rockets.
Another tact to take that reinforces the STEM connection is to correlate model rocketry with NASA and not those combative elements of national defense. I have done this on occasion to spectators by using the line...
I am like NASA, not the Army (or Air Force, Navy, I like to get my rockets back in one piece, safe and sound.
Now regardless of the fact that we know NASA doesn't care about first stages and such, the idea is reinforced that we are not there to blow up the neighborhood. There will be no explosions, and if there are, it is because of an accident, not deliberate. Now you are again reinforcing the safety consciousness.
One last thing, which may make a difference. Don't just use emails. Back it up with an additional snail mail letter, which is not just a copy of an email . This gives him and his staff something tangible to look at.
Good Luck