system
Given the following post, respond as if you're commenting on Reddit:
human
[Judge Dredd] If Mega City 1 is so overpopulated why do they continue to allow children to be born?
gpt
People die, you need new people; ain't much of a society if it disappears in 60-90 years.   This rules out actual solutions like contraceptives or gene alteration treatments in the water/air/etc. 

So you get left with legal mechanisms, but the population is huge and the enforcement teams are tiny and also dealing with every other crime.  

And what do you have Judges do about illeagal births? 

Have them stomp the mewling tots as an illicit good? 

Sentence everyone involved? that seems over reaching even for a megacity authority.

Gun down the lawbreaker parents and drop the bundles of humanity at an orphanage? that might halve the population if you can track down both parents.

Jail the parents and send the child for adoption, the prison system is already at its limits and, being a driving instinct, this is a crime most every human is likely to break given half a chance.

Do you get natural illeagal citizens? 

 The city is a conservative dream city (literally a parody of British conservatism) with highly stratified class systems and a 'by your own bootstrap' economic model. 99% of the populace is living in squalor with no hope of that changing, they have no interaction with the social classes that define society or pass laws and zero impact on the lives of that group outside of violent crimes and robbery.  The ruling class like it this way, they have someone to feel superior too and lord over and a constant threat to isolate themselves from.

The simplest solution to population problems for the ruling class is to just ignore them. At some point somthing infectious will solve most of the issue.