Your roommate leaves for the summer and sublets their room to a friend, but the sub-letter simply isn’t paying rent. Can you evict them?
This recent Chicago Tribune article gives some legal background about the topic. According to the article, you could probably technically evict them (so long as sublet was above board in the first place), but getting everything taken care of in time probably won’t work.
The best way to avoid this situation is to have your original roommate pay the rent to you, and have their sub-letter pay them. Of course, it’s best to make sure your roommates only sublet to people you know and trust. But that ideal is not always possible.