We’ve also changed how AI acceptance works for federation laws, so that it is more transparent and more consistent with other features in the game. We look at the AI attitude a lot more now, and it will affect which laws the AI is attracted towards. For example, militaristic empires, or those with either Honorbound Warriors or Federation Builders personalities will be more likely to accept a higher fleet contribution law.
Generally speaking, the best way for you to pass new federation laws is to get the Federation Cohesion to 90 or above, and then suggest a new law change.
When it comes to suggesting changed, the AI will still not attempt to suggest changes very often, unless they are the federation president.
The AI will generally not want to increase Centralization unless Cohesion is 90 or higher. Cohesion also directly affects the acceptance chance by a factor of x0.25 (100 cohesion equals +25 acceptance).