Central to Kelsen's theory is the Grundnorm, or Basic Norm, which serves as the hypothetical posited starting point of a legal system. This Basic Norm is the foundation that makes possible an entire system of law-a system in which all laws have authority. Every law in a system is valid because it can be traced back to this Basic Norm.

The Basic Norm is not something which a government or legislature creates; it's an assumption, an underlying postulate that we must accept if we want to make sense of the legal structure. It's like the basic rule in a game: without it, the game wouldn't work. For example in a democracy, the Basic Norm would be something like "one ought to follow the constitution"; that is to say, every law made under the constitution is valid.

We Need the Basic Norm because without it, we would not have a foundation by which to ground the reason for the validity of laws. We would be left with an endless progression of "why is that law valid?" "Why is the source of that law valid?" The Basic Norm ends this cycle by being the ultimate source for all other validity claims.

For example, in a newly formed state, acceptance of the first constitution would constitute the Basic Norm, empowering all the laws and court decisions enacted under it.