How was the government system in Gaul?

[Andy]

The magistrate you refer to is termed Vergobrate, elected to position. But above this person, like in some parts where a king still ruled (such as the Euburones who were ruled by two kings) the Druid was above this position, so the king/vergobrate did not have unlimted power, more I believe they were a public face/puppet of the druids.