Title of the track is a term of war and politics.
The expression comes from Latin and it used to describe an act that justifies war.
Casus is a masculine noun which can mean case or incident or even rupture.
Belli is genitive case of the word bellum - belli means of war.
The event or act itself used to justify war is often fabricated or embellished.
In World War II Hitler used the policy of lebensraum to justify the annexing of neighbouring sovereign states.
The Soviet Union staged the artillery shelling of a Russian village of Mainila and blamed Finland for the aggression.
This was used as a casus belli for the Winter War of Finland 1939-1940.