A conflict with the interests of a former client is one of the most frequent bases for a disqualification motion. In addition to the potential violation of Rule 1.9 and other ethical rules, these conflicts risk that the lawyer will (1) use the former client’s confidential information to advance the current client’s cause, (2) pull punches for the former client (and thereby dilute the representation of the current client), or (3) attack her own work product. These risks, and others, frequently cause courts to consider the lawyer’s disqualification. The key question is often whether the former and current matters are the same or substantially related. If so, the lawyer or law firm is usually disqualified (absent significant equitable considerations counseling against disqualification); if not, the motion to disqualify is typically denied because the ethical rules are not violated and the policy concerns listed above are not directly implicated.
 Model Rules R. 1.9(a); Richard E. Flamm, Lawyer Disqualification: Conflicts of Interest and Other Bases §7.2 (2003) (discussing Rule 1.9 in the disqualification context and citing cases). Although the rules differ in their details, addressing the conflicts of former government lawyers and judges often involves overlapping analysis. See Model Rules R. 1.11, 1.12.
 See, e.g., O Builders & Assocs., Inc. v. Yuna Corp. of NJ, 19 A.3d 966 (synopsis) (N.J. 2011) (“[The court held that the] restaurant owner failed to establish that matters disclosed during prior consultation with opposing counsel were the same or substantially related to the present suit, or that the information disclosed was significantly harmful.”); see generally Disqualification of Attorneys for Representing Interests Adverse to Former Clients, 64 Yale L.J. 917, 918–19 (1955) (footnote omitted) (“An attorney may be disqualified from litigation if his participation would violate his ethical duty to a former client. For the last hundred years courts have been expanding the obligation owed former clients, broadening the area of employment prohibited to the attorney. At the same time, developments in legal practice have often made disqualification from even a small area of employment an increasingly severe sanction. The clash of these two trends in a number of recent cases suggests the necessity of reexamining the scope of the duty owed by an attorney to his former client. Disqualification rules were fashioned at common law to assure the public that any information confided in an attorney would never be disclosed or utilized adversely without the client’s permission. Such a guaranty was deemed necessary to encourage maximum disclosure of all relevant facts, a prerequisite to adequate preparation of a client’s case.”).
 Model Rules R. 1.9(a) (prohibiting adverse action against a former client in a matter substantially related to the former client’s matter); see also id. cmt. 3 (“Matters are ‘substantially related’ for purposes of this Rule if they involve the same transaction or legal dispute or if there otherwise is a substantial risk that confidential factual information as would normally have been obtained in the prior representation would materially advance the client’s position in the subsequent matter.”).
[Source: Keith Swisher, The Practice and Theory of Lawyer Disqualification, 27 Geo. J. Legal Ethics 71 (2014)]