This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
衑 combines 行 (going, road) with 令 (order, command). The exact historical development is uncertain, but it likely relates to a path or way, possibly a specific type of road or a commanded route.
The outer 行 suggests a road or path, and the inner 令 looks like an order being given. Imagine a road that follows a strict command, but since the meaning is uncertain, treat this as a visual hint only.
For レイ, picture a ray of light shining down the road (行) as a command (令) is given: ray -> レイ.