If a rabbit jumps straight up in the cabin of a high speed train, according to the law of inertia, it will land in the same place.
It's both a law and a rule. This usually refers to something that is a physical law, but also can simply be a law, too. Anyways, lots of rules. Lots of laws. It's both, so the stronger one (law) takes precedence.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.