Wish I was at home so I could post a screenshot... ok so for a planet  you can get the buffs on them, either the planet just has them or you find when you explore... like an entertainment hub that increases culture spread rate or security protocal that gives you more tactical slots.   There is one called Fallout, which is supposed to limit the population cap on that planet to 30.  However when you do planetary research into population, you can increase the population on  a'fallout' world just like it wasn't there. 

Yup, it should reduce the maxium allowed by 30, it doesn't set the maximum to 30 The red is like a negative sign, the green a plus So Fallout would be -30 pop!