The nutshell of the law; must be 18 to buy. Must be 18 to own. Cant use it unless the legal owner is present. Cant play most anywhere until you are 18.
Playing anyway on un-authorized land can (and will) get you in very deep shit. Playing with something you cant legally own (unsupervised) is not smart or mature.
Read some more of this website, all that is already written down.
Following laws shows maturity. Legal Responsibility for yourself starts at 18 in this country.