Whether they were over the line is rather irrelevant. You can't take people hostage for drifting over the line. So the Iranian justification is ridiculous.
I had a neighbor who shot a man in the street because he thought he was a peeping tom. He tried to explain to the police that it was definitely the peeping tom but the policeman retorted "You can't shoot a man in the street PERIOD. Whether he was a peeping tom is irrelevant"
But you can shoot a peeping tom if he's armed and standing in your living room.
-Devil's advocate.