Journals go through some procedure to be indexed by ISI as IF journal and with the condition that Self Citations should be not more than 20% for consective two years. If they are so Thomson Resuters removes the journal from the IF journals list, which is also called journal is black listed by researcher community.
I have a question why the authors are also not black listed based on doing selfcitations more than 20% of total. I know people started group citations, and other tricks like making 3 group of publishers and not self cite but cite each other.