
All laws are more powerful the local laws, a good way of thinking of it is like the relationship of US federal government to state governments.

Power of the purse, levy taxes and spend money
Relegation will balance the play field to not undermine the economy - to prevent bubbles in the economy and cause real growth
No tariffs - free trade for all
One currency - so simple
No social or moral or religion issues
World police force enforces all laws including human rights, has power to go anywhere to enforce laws about rights and private protection are still around (right to trial and other protections)
Crime can be hunted everywhere - can not run from the cops

Global warning action can be taken if wanted
State sovereignty does not exist