Another unprecedented update coming through my wife's network just now - CBP in Blaine, WA just rejected a couple of LPR's who had just gone across the border to visit a specialty food store in British Columbia. (Due to OFAC restrictions, the ethnic groceries in Canada tend to be a bit better stocked with authentic Persian items than those stateside, so it's a common trip for Persians in the Seattle area.) CBP told them that they should plan to hang out in BC for at least the next 3 months. CBSA apparently readmitted them to Canada without incident, which I suppose at least puts them in a better position than those in airport detention right now.