Quote Originally Posted by Rubber Ducky
If the population is going out of control above 24k put em to the sword

1) Empty the city of all units and park em just outside.
2) Give city to enemy (or some faction you're willing to go to war with). Offer it as a gift.
3) After changed hands, reoccupy and slay them all!

I find this the most efficient way to maintain order and gain huge amounts of cash of loot. It wouldn't hurt much in taxes in the long run as someone proved that population above 12k I think pay much less taxes per.
Why don't you just let it go rebel? They are less likely to field decent units.