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I am sorry you had to deal with some knot head filing such a complaint, since it is not illegal for you to take pictures of planes as you see fit. I am afraid that the city knife law applies to any concealed carry of a weapon, no matter how slightly concealed. Having a knife for "protection" is not enough, you have to argue that you need the knife in your profession to open film boxes and open film cannisters and for your photography occupation, and that would be a reasonable defense and in most cases like what you are describing, the MA city attorney/solicitor will throw out the charge against you when you go to court and plead not guilty.
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