who had the power in the California Mission, and how was it in force?

Answer 1

The California Missions were built under the command of Catholic Spanish Missionaries. The Missionaries were there to convert the local Native Americans, religiously, so that their government may take control of their lands without too much resistance. The Missionaries and the Military were a two-part method of colonization in the new world.

To answer your question, the Alcalde (mayor) oversaw the entire operation locally, while the Spanish "Fathers" (Missionaries) had more isolated control over the Missions and their perspective inhabitants.

Answer 2

The padre, or head priest maintained all of the power in the mission. Sure, there might have been a few soldiers at some or most of the missions, and by a few I mean less than ten, but the real power and authority came for the head priest at each mission, and even they were under the authority of the President of the MIssions, Serra at first followed by Lasuen (sp?).

Some of these missions were indeed fabulously wealthy. They owned tens of thousands of acres of land, tens of thousands of head of cattle, and the had Native Americans who did virtually all of the work for them, living in near slave-like conditions. Sometimes discipline was enforced with the use of the rod and whippings, and sometimes the Native Americans rebelled. But generally, the mission padres and the Native Americans lived together in a cooperative relationship that ultimately led the to wealth of the missions and the destruction of much of the local native culture.

When the missions were eventually secularized after the 1821 independence of Mexico from Spain the wealth of the missions was distributed widely to favored ranchos.