You can add your legal question and concern by using the "edit post" feature to add content to your first post or you can "reply to thread" and add content that way. The "preview post" function on this site is on the blink and it tends to delete content rather than post it, so the failure for your content to show is the site's failure and not yours.
Based strictly on the
title of your post, though, I can tell you that many people assume they are not "in possession" of drugs or alcohol if the alcohol or drugs do not belong to them - and this is not the case. A person can be charged with possession if the drugs or alcohol are within their control (in the same car or in the same room; reachable).
Here is a link to Utah's minor in possession laws:
http://le.utah.gov/code/TITLE32B/htm/32B04_040900.htm
It is to your benefit to speak to an attorney in your area.