Why Iran doesn't make a list with all Iranian outside engaging in treacherous activities names, remove completely their Iranian nationality (if they have) and never authorize them to get back even to see their families or their graves?
Double nationality entities coming in Iran represent a way bigger threat of spying/engaging in nefarious activities than a simple American or whatever tourist without the Iranian double nationality.
Iran is giving them the opportunity to spy by letting them having Iranian nationality and passport
Checking their activities and forced investigations, list names of Iranians working for BBC or other destabilizing groups, if they are engaged in such activities:
\- Remove their Iranian nationality, nullify their passports, just keep their birth certificate, close all bank accounts they have, seize all their assets and sell them, make such as they aren't existing in Iran beside they are born here
\- Reinforce customs, laws and check of their baggages
For airports, check every double nationality specially coming from UK, Dubai (Iran International operates with UAE based reporters), USA, Canada, Australia, Sweden, Albania
Check all their mobile phones and laptops, request for their passwords and look into it if they follow or support any of these channels or hold the same ideas
If they do not comply with giving their passwords, they will be exported back and proceeded with their destruction of Iranian identity and passport
\- Don't give them the right to get out of the airport and give them the option to take the next plane to get back where they came from (at their cost), and make a special room in airports so they sleep there until they can get back and buy a plane ticket