Is the city In Decline and has only a few turns before it vanishes?  If so, anyone can assimilate the city without needing to be a patron.  If that's the case, then it's working as designed (I'm still not sure how I feel about it, though).

I guess it's working as indended then.  The city was in decline.  It seems strange that I could assmilate it.  I had contributed nothing toward patronage and my enemy was at 100 patronage.  I never noticed this behavior before.  

I don't understand why the mechanic is this way.  Why couldn't the city just disappear and leave ruins?

They're falling apart and their elites are jumping the ship. That's an easy target for assimilation.

Maybe it could be changed so that to assimilate them you'd need at least Tolerant relation with them, or 'free' assimilation could be done only by bordering nations, I don't really mind it, though. If we'd ever get some special traits for assimilating IPs, maybe as a penalty it could be not given for assimilating ones in decline.

DNLH wrote:

Maybe it could be changed so that to assimilate them you'd need at least Tolerant relation with them, or 'free' assimilation could be done only by bordering nations, I don't really mind it, though. If we'd ever get some special traits for assimilating IPs, maybe as a penalty it could be not given for assimilating ones in decline.

Yeah, I could see any of these restrictions feeling good.

I'd also love to see some factor where an empire with 100 Patronage (or higher than you) is notified when a "newcomer" attempts to assimilate an IP in decline, and the empire with full/high Patronage has "first right of refusal" to assimilate it themselves, can pay influence to veto the assimilation, or that this triggers some sort of "bidding war" to assimilate the IP with a benefit/discount in the bidding war for existing patronage.  (Long story short, I'd love to see more done with IPs overall.)