A Mexican mother, in the US illegaly, has claimed sanctuary, in a Chicago church. See this LA Times article for more details. The Times article gives a cursory overview of the history behind this but there's so much more there. Rob Meens has a recent article in Speculum (2007) on this, and Sam Collins has a great dissertation from Berkeley dealing with sanctuary under the Carolingians (which hopefully will become a book soon) that I'd recommend for further reading.
What's interesting is that it's worked (so far). She's been there for over 9 months now and Homeland Security has refused to enter the church to take her. Seems that knowing your medieval canon law comes in handy. See your local medievalist for more.