One way of deriving laws of energy, impulse and angular momentum of electromagnetic field conservation is following:
Introduce two values below: $$ \mathbf P = \frac{c}{4 \pi}[\mathbf E \times \mathbf B], \quad W = \frac{1}{8 \pi}(\mathbf E^{2} + \mathbf B^{2}). $$
Using Maxwell's equations and time derivative of these values, get the laws.
But how to argue an introduce of values from it. 1? Can Noether's theorem help to argue it?