There are three stages to this process.
Stage 1: Can the PCB produce a document signed by a BCCI official commuting to several series?
If no, BCCI wins.
If yes, Progress to Stage 2.
Stage 2: Can the BCCI produce a contemporaneous letter to the Government of India requesting permission to play Pakistan?
If yes, proceed to stage 3.
If no, PCB wins.
Stage 3: Can the BCCI produce an official letter from the Gocernment of India prohibiting the series?
If yes, ICC Disputes Committee must determine whether the written commitment is invalidated .
If no, PCB wins.
By the way, if the PCB does win, the ICC will remove the damages from the BCCI’s annual payment from the ICC. Everybody knows the BCCI wouldn’t write a check: the ICC would just removed the money from the BCCI’s annual welfare handout.