The preamble of the Constitution is the part through which the US constitution establishes that the government derives its power from the people. It also introduces the six motives of the government in serving the people.
The fundamental purposes and guiding principles are briefly stated in the preamble. The preamble of the US Constitution does not serve as the power provider to the fundamental government neither it put some specific limitations on the government's action. Due to the limited or restricted nature and due to this no court has ever use it as a conclusive factor.