That's in the text of EC261 and applies in all cases. So you aren't able to avail of protections from EC261 if you don't have the right documents, or your are reeking of alcohol or turn up too late. Separately there is an extraordinary circumstances clause, which airlines rely on for delays and cancellations, which relates to events not under airline control such as weather and ATC. This greatly over-used clause cannot be used for IDB or downgrades. My take on the cases raised here is that the passenger had the right documentation but the process failed, at the HAL end. If this caused a delay then it's not claimable (unless BA failed to use all reasonable measures); but if it's IDB then BA cannot rely on it being a HAL event and it is claimable. Moreover there is a specific clause in EC261 which indicates that airlines can push the bill on to HAL but it's the airline that the passenger must deal with, not HAL.