The disfellowshipping practice did not become official policy of Jehovah’s Witnesses until the early 1950's. However, in 1947, just a few short years before the introduction of this policy, there was an article published in the Awake! magazine that criticized the Catholic Church for their practice of excommunication.
In the early 1980's, in an effort to squash any form of dissent, the policy of extreme shunning of disfellowshipped members of the congregation was extended to include those who have disassociated themselves of their own accord from Jehovah’s Witnesses. Now, they were to be shunned, as well.
Since at least the early 1980's there exists no civil way to leave the organization.