If your B-I-L wants a cold one while on the trail that is fine, just as long as what ever he packs in has to come out. The old phase "pack it in - pack it out" sure applies every time you go into the back country. I would imagine that there will be some sites out there where he can dispose of trash properly. Including human waste. I say that because even in areas like Rainer NP, and North Cascades NP there are areas where you have to pack out your human waste.
The National Park Service has moved in the direction of handing out waste bags to hikers and campers going into wilderness areas. I know this because I personally handed out a lot of them of people going on the PCT and PNW-T. I wish I could show you some pictures of some of the twenty-somethings when I had to tell them to pack their waste out to a disposal site and then give them some bags. They looked as though I took their favorite toy away from them.
If your B-I-L is starting out at a National Park ranger station, he will probably have go in and and ask about permits, weather conditions, trail reports, etc. That's the best way to find out the most current up to date info before heading out. If he's going to stay at a campground, the NPS has a computer registration system that can actually find out if campgrounds are full or not. If some are full, the staff will know which one will be open by the time he reaches them, or if some are open he could reserve a spot for a night. NOT ALL NPS RANGER STATIONS CAN DO THIS
. If he does stop at one he more an likely will given waste bags.
I mention weather reports because more people get lost or injured when the weather changes unexpectedly. Mostly because people did not prepare for sudden changes. Oh, and the alcohol......moderation is the key.