Former Oak Bluffs police chief Joseph C. Carter has been sworn in as adjutant general of the Massachusetts National Guard by Gov. Deval L. Patrick.

Mr. Carter, who holds the rank of major general, commands the nearly 8,000 members of the Massachusetts Army and Air National Guard. He is the senior military advisor to the governor of Massachusetts.

Mr. Carter became police chief of Oak Bluffs in 1998. He resigned in 2003 to become chief of the Massachusetts Bay Transportation Authority police department.