In 1996, Congress passed a set of sweeping changes to the immigrations laws, collectively known as IIRIRA. These changes imposed immigration consequences for many actions (including certain criminal convictions) that did not previously exist. The Supreme Court has ruled that individuals who lawful permanent residence and subsequently committed a crime before the passage of IIRIRA would not be subject to the retroactive applications of these provisions. The Ninth Circuit, in an unpublished decision, held that the laws would not apply retroactively even if the criminal conviction pre-dated the acquisition of residency (and thus, may have called into question whether the person was ever entitled to residency in the first place).
The decision has very broad language: "Of course, in the cases just cited, the alien had become an LPR before he committed a crime, whereas Serrano committed the crime in question before he became an LPR. But that is a distinction without a difference. We have held that where an alien had committed a crime but applied for immigration relief before IIRIRA became effective, application of IIRIRA’s provisions to the alien would be impermissibly retroactive. If the mere filing for a form of immigration relief precludes retroactive application of IIRIRA’s changes, it follows as the night the day that actually obtaining LPR status before IIRIRA’s effective date precludes retroactive application."
The language could be potentially useful for lawyers arguing against the retroactive application of almost any of IIRIRA's provisions, even those that do not involve criminal convictions.
The full text of Serrano v. Lynch can be found here: http://cdn.ca9.uscourts.gov/datastore/memoranda/2015/07/22/12-70568.pdf