Use the noun anarchy to describe a complete lack of government — or the chaotic state of affairs created by such an absence. A substitute teacher might worry that an unruly classroom will descend into anarchy.
From the Greek for "without a ruler" we get this word for the political philosophy that the best government is no government at all — a movement that enjoyed surprising success worldwide in the early and middle parts of the twentieth century. Today, the word is more commonly used to describe not a political ideal but a state of total disorder, chaos and even violence: "A type of bloody anarchy is beginning to reign." A good synonym would be "lawlessness."