Region: Communist International League
In answer to your question FSC the SSS,Revolutionary Vietnam and Republican Spain chose to leave the region as :
They were not prepared to subsume their nebulous idea of "sovereignity" (read "regionalism) for the greater good and pledge to protect their fellow comrade regions
The will tell you that they have participated in Solidarity actions, but before you take these at face value, you should first investigate the circumstances behind their intervention - but do not take my word for it speak to those we fought alongside them.
They also seemed to be obsessed with the idea that they would somehow be compelled to participate in "offensive" actions, such as those undertaken by Antifa & The Red Fleet, despite reassurances to the contrary.
So vehement were their opinions on this matter that their subsequent vocal attacks on those that advocated action rather than promises swiftly degenerated into what can only be termed as name calling and abuse
Not content with driving away allies with this approach, they then turned on the founder itself, announced that they were leaving to form their own organisation, and then had the gall top demand that the LI was "locked down" to prevent it falling to hostile elements.
This apparent contradiction "we wont protect this region but you should and we demand that you do so" revealed them has having no true interest in interregional co-operation, but rather promoters of their own self interest - no-one forced them to join, but after their behaviour we would be highly unlikely to invite their participation until they have matured and realised that insulting people does not influence positively