Black Flag gets you a DSQ without a hearing even if the race is restarted. Some RCs will give you a warning by throwing the black flag, then postponing, then restarting the sequence with the I or Z flag, letting you know that they have the black flag on the boat and ready.

General recalls can happen after a black flag, but unless changed in the SIs, the RC has to display the sail numbers of the BFD'd boats so they know they're not supposed to start - if a BFD'd boat starts after her number is displayed in the restarted race, she gets a BFDc, which can't be dropped.