Roman Divorce-by-Separation

David Instone-Brewer makes frequent reference to the unilateral divorce that Paul was trying to prevent among Christians in 1 Corinthians 7. Instone-Brewer calls it a divorce-by-separation. Unlike the legal term used by the Hillel Pharisees for their form of groundless unilateral or the "Any Cause" (1, 2, 3, 4) divorce, there doesn't seem to be one for Roman law. A chapter from a monograph "Marriage Divorce, and Children in Ancient Rome" (1991) describes the historical aspects of Roman divorce in the late Republic, early Principate. Divorce Roman Style: How Easy and how Frequent was it? (pp31-47) by Susan Treggiari describes the process.

pp. 33-34
"If the initiation and continuance of a marriage depended on consent, explicit or implies of both spouses ..., then it follows logically that divorce may be produced by the withdraw of that consent by one of parties, or perhaps we should say, more positively, by the decision of one party not to retain the relation"

p. 36
"No ratification from any outside authority (such as Church or State) was necessary for divorce, any more that it was for marriage."

p.37 top
"Just as documentation of the action of the divorcing spouse was not legally necessary, so receipt of the notice by the husband or wife remained inessential."

p. 37 bottom
"As far as the legal system went, by the time of Cicero it appears that both husbands and wives could divorce each other, unilaterally, without seeking outside ratification."

This is the Greco-Roman unilateral divorce that Instone-Brewer describes in his many works. Paul refers to it in verses 10-16 in 1 Corinthians 7.