The easiest way to do that is to add this line of code just after the <in>!movie %PARAM%</in>
<out type="break" condition="!=" lvalue="%USERMODE%" rvalue="@"></out>
Basically what this code is doing is checking the users mode in the room, it can either be blank, a + or an @ just like you see in the chat rooms. The condition value here is != which means if the usermode does not match @ then the script will "break" meaning stop. So by placing this piece of code at the top of the script where you add files you're making the script check that the user performing the command has an @ in the userlist and if they don't it won't allow the script to run.
Something to note about this is, if you're using Metis 2.80, 2.81 or 2.82 this won't work. You need to use Metis 2.83 or better. If you need such a Metis you can use my distribution of Metis that you can get here: http://www.mxpulse.com/board/viewtopic.php?f=9&t=405
You will only need to download the metis.r2x and replace the one found in your plugins folder then restart your bot. I recommend you backup your old metis.r2x (don't leave it in the same folder or rename it, physically move it to another folder) just in-case you need it