Borders can remain open too. You need to spend resources from the budget to keep your borders closed.
Border price will increase every minute by 0.01% (from the starting level) if more than 90% of regions have closed borders.
Border price will decrease every minute by 0.01% if less than 90% of regions have closed borders.
All this can be regulated by passing the specific laws.
|Resources||Spendings (for 1 minute in 1 region)|
You can navigate to Maps and select a filter, which will show where the borders are closed and where they are opened.