According to ▲Church Faith, Physical Law is substantial order. This first law is essentially energy’s structure of physical substances in space and time. It never changes and its changes significantly affect material need.
Physical Law is fundamental-rule governing existence parallel to and without being affected by acknowledgement. Matter is subjected to its expressed control. And when nothing is said to be present then recognition is necessary to initiate the energy that makes it matter.
Physical Law is commonly physics. Today, physics is presence to the atto (10-18m). Observation of the structure and behavior of everything with enough significance to be present including life and the mass-less properties created by life is science. Science incorporates thermodynamics, chemistry, mechanics, electricity, radiation, and acoustics. When science pertains to properties of life it includes mathematics and logic, biology including physiology and organic molecules, and social subjects like psychology, sociology, and economics.
Physical Law never changes but the identity of observed phenomena affects how we describe its expression. As ideas (like nuclear power) become useful employment of historic resources (like coal) turns useless. And when Physical Law includes social science it’s written in terms of metaphysics!