There are a few queries each week regarding the capital city, leader and religion fields and typically over when they can unlock the fields and what "Awaiting Legislation" means for them.
There are three customizable fields in your Settings that are greyed out when you first create a nation. These settings may also be greyed out for nations that ceased to exist before the fields were introduced.
The population requisite is straightforward. You need x-number of citizens to qualify for the issue. That will change when your population is high enough to "Unlockable: Awaiting Legislation".
EDIT: As per this post nations now receive the relevant "unlockable" issue as soon as they qualify for it, instead of having to wait for it to be randomly selected. Receiving the issue does not automatically unlock those fields. You need to vote on the issue. If you dismiss it or pick an option that is against any of these elements, the field will remained grey out. As issues do repeat and you either picked an option to not have religion, a leader or city, or simply decided to dismiss it but now want to fill in those fields, you just have to wait for the issue to reappear.
It was noted here that some times player either decide not to have daily issues or have checked off 'Vacation Mode' in their settings tab. If this is the case, in order to receive the issues for national capital, leader and/or religion you will need to uncheck that box or enable at least one issue per day.
If you wish to view the issues before you get them, or ask questions, you can click any of the links below, which will take you to the NationStates Issues **SPOILER ALERT** thread.
Capital City: Unlockable with 250 million citizens.
#241: A Capital City For @@NAME@@?
Leader: Unlockable with 750 million citizens.
#242: Follow The Leader
National Religion: Unlockable with 1 billion citizen
#243: A Question Of Faith
