This law says that the mass and energy cannot be created or destroyed. They can only be transformed from one form to another form. This is a law of nature and physics.
It can be shown that many laws of physics are either same as the LOC or can be derived from the LOC. Thus the nature has only one kind of law, the LOC. In particular, it can be shown that Newton’s second and third laws are LOC. The second law of thermodynamics is a LOC. The conservation of momentum can be derived from the LOC. Even the derivative theory of calculus is a LOC. Thus the entire theory of differential equation is based on the LOC. Since all systems can be represented by differential equations, then all systems naturally obeys the LOC. In this paragraph we have ignored the relativistic effects.
Economy is a system also. Thus it must obey the LOC. It does not have to follow all the laws of nature and physics, but it must follow the basic law, the LOC. If we can ensure that, then everything will be normal and natural.