You mention MLL so I'm assuming you're departing on a domestic/international ticket.

Also assuming that you are checking your bag with a major airline whose check-in counters are open all day-long after arriving in YYC. You mention MLL so it's gotta be AC. yeah, they're open all day

So you can easily go in and out of the domestic/international area (A thru D gates).

The boarding pass rules are that it can't be scanned at security screening in too quickly of succession, but I've tested those limits and "quick" is more like 5-10 minutes between scans before failing on the second scan. On the failed attempt, they just ask for your ID, you don't even need to explain why you went thru twice

I do this all the time (after standing by on an earlier YEG-YYC flight to maximize the YYC layover) for the same reason you do (to see friends!) good luck! heck, if you're near the MLL when you land, grab a drink or three while you wait for on the way to get to bags

fysloc