The first law decreed by the new Emperor simply stated that no kingdom under his rule could contradict his laws. Each King was free to oversee his demesne as he saw fit, however he wouldn’t have the authority to thwart the Emperor’s wishes. This first tenant of our budding society established the notion of Imperial Primacy.
To ensure compliance with the first law, the Emperor then made a second decree: Henceforth every Kingdom was required to maintain a record of the Imperial Laws within its capital, available for public viewing, engraved upon slabs of granite. Refusal to comply was treason.