Repetition

[HaraKiriBlade]

Countries that allow their citizens to bear arms experienced drop in crime rates whereas countries that do not allow (their citizens to bear arms) experienced the opposite.

Is it ok to take out the the part in brackets?

[Anglika]

Yes - would read better too

[mykwyner]

You would have to replace it with a pronoun. Also, do not mix tenses, and watch your subject-verb agreement.

Countries that allow their citizens to bear arms experience a drop in crime rates, whereas countries that do not allow this experience the opposite.