They are empowered to establish and regulate the interrelationships of the people with their territorial confines, the relations of the people with the community as a whole, and the dealings of the community with other political entities. Plus, all of the other governing bodies in the world, such as the monarchs, dictators, and all in between.
Government also includes the people who form the supreme administrative body of a country as well.
They were the ones who established the idea that constitutional law was superior to ordinary law. They were on their way towards a good, long lasting government. But all good things come to an end, and Rome was one of them. However, all was not lost. It wasn't until the 16th century, when the nation-state became a definate form of government.