Explain why the observation that the sun sets in the west could be called a scientific law.

      Best   A scientific law is a statement of a relation that expresses a fundamental principle of science.

The sun sets in the west on Earth and most of the planets in our solar system.
So it could be considered a law on Earth.

But the sun doesn't set in the west on Uranus, since Uranus's axis of rotation is tilted by about 90 degrees to the ecliptic.
And there is no scientific evidence that all other planets (over 570 known so far) rotate from west to east (which would cause their sun to set in the west).
Some planets are likely tidally locked to their star and the sun on those planets NEVER sets