But how often do Lukashenko and his circle actually fly out of Belarus anyway? He already had no problem with closing his own borders before anyway, so it's not like this is going to seem like a strong move to him and it only really hurts the Belarusian people.
If you are a Belorusian elite with kids in US and UK schools, money in Switzerland etc, living comfortably so long as Lukashenko is president. Then suddenly your assets are frozen, and your children can't travel to London when their next semester in the very expensive school starts. All because Lukashenko had to discipline some kid. You aren't going to be happy about that little stunt, and Lukashenko will be told.