你好.应该是：it not only is legal, but also doesn't hurt anyone,(请注意is的位置)
因为not only 修饰 is,but also 修饰 doesn't hurt. 所以要把is 放到not only的后面
也就是说,not only,but also修饰各自的动词 或者是：
it is not only legal, but also harmless to anyone, (请注意is的位置)