Uncaught TypeError undefined is not a function when called outside of jQuery

Question

I'm trying to figure out why when I call setupControlBox from within the $.getJSON call it works (in the if condition) but if I call it from the else condition it throws an undefined error (I set opts.load_url to false). Does the call have to be encapsulated in $.someFunction()?

// Load existing form data

if (opts.load_url) {
    $.getJSON(opts.load_url, function(json) {
        form_db_id = json.form_id;
        fromJson(json.form_structure);
        opts.loaded(json);
        var controlBox = setupControlBox(opts.control_box_target);
    });
} else {
    var controlBox = setupControlBox(opts.control_box_target);      
}