18-22 year old's in college are self-contained for the most part. They're around people their own age, not known for intermingling with senior citizens etc.
In Boulder the area that students living off campus is called the hill. It happens to be surrounded by the most affluent (read old) portion of Boulder. I’ve seen gangs of students walking up and down Pearl Street with no masks. The students are not isolating
The people in your scenario that are most at risk are roaming the same area freely, so the solution is to ban the least at risk people?
The same people who are the least likely to follow the prohibition?
If you want to protect the most at-risk people and the only way to do it is to divide the high-risk & low-risk the far more logical route would to ban the high-risk people.
CU has a lot of elder care and nursing homes near it. These people are in poor health to begin with. Covid is not doing them any favors.
I know this because I have family in those facilities that I have not been able to see since this all started. We (low risk) have been banned from these facilities (high risk) for months now.
We are lucky in that we are still somewhat healthy in regards to my family near CU. Many other families in these facilities are not and have lost loved ones due to the pandemic. The bans are not working as well as hoped, especially since the start of the school year.
The decisions of the CU community in relation to the larger Boulder community are contentious at the moment. Many parts of the larger Boulder community do not appreciate CU's 'cavalier' policies.