In the so-called common-law countries (or common law adversarial
system, or common law jurisdictions) are prosecutors members of the
(state) bar? If so, is that a requirement?
If so, does that mean that they are somehow under the bar's
disciplinary jurisdiction?
The Practice of Law is Mostly State Regulated
Almost all prosecutors are (and must be) admitted to the practice of law by one or more state courts or the practice of law in D.C.
Prosecutors in state courts must be admitted to the practice of law in the state in which they are employed.
Law Clerks
Sometimes a prosecutor's office or law firm will hire someone who has graduated from law school to be a lawyer and has them start work before they pass the bar exam. But, until they are admitted to practice, they are only allowed to work as "law clerks" (i.e. basically they can do what a paralegal can do).
Admission On A Case By Case Basis
It is also not uncommon for someone admitted to the practice of law in one place to be admitted pro hac vice in a particular court for a particular case where they are not admitted to practice, especially in federal court. But, sometimes this requires sponsorship or affiliation with a lawyer or law firm admitted in that jurisdiction.
I have also encountered one case where I non-lawyer was granted special permission to represent someone in an appellate court proceeding, in which the non-lawyer was the manager of the client, even though this is usually not permitted in appellate courts.
Integrated v. Non-Integrated Bar Associations
In some states there is an independent state bar association and the state supreme court handles admission to the practice of law and discipline for violations of professional ethics and requirements. In other states, there is what is known as an "integrated bar" and this function is handled by the state bar association and the state supreme court merely requires that someone be a state bar association member in good standing to practice law. Functionally, the two are basically indistinguishable from a lawyer or prospective lawyer's perspective.
Multi-Jurisdictional Practice Of Law
There are also fairly elaborate rules governing when someone who is admitted to the practice of law in one state is and is not considered to be practicing law in another state without a license.
The Practice of Law in U.S. Federal Courts and Agencies
Each federal court in the U.S. has its own separate bar, as does the U.S. Patent and Trademark office. But, a membership in the state bar (or the D.C. bar) as the case may be is usually a prerequisite to admission.
A federal court will often also admit to practice before it a federal government employed lawyer who is admitted to practice in a different state than the one where the court is located.
Admission to the bar of a federal court is usually granted as a matter of course to people admitted to the practice of law in the relevant state, and without too much fuss to federal government employees admitted to the practice of law in another state or D.C.
Patent Law and Tax Law
The U.S. Patent and Trademark office has its own bar to which someone practicing before it (which is called prosecuting patents and means obtaining patents for people from the USPTO) must belong. There are two paths involved.
One is to be admitted to the practice of law in some state or D.C., and also requires special science based knowledge and patent law knowledge in addition to general legal knowledge and to take the USPTO bar exam that patent agents take. If one takes this path, one can both help people to obtain patents from USPTO and litigate both patent and non-patent matters in courts where the attorney is admitted to practice and in USPTO proceedings.
The other path is to become a registered patent agent without going to law school or being admitted to the practice of law. This still requires special science based knowledge and patent law knowledge demonstrated by passing the USPTO bar exam. If one takes this path, one can both help people to obtain patents from USPTO, and litigate in USPTO proceedings, but one cannot litigate both patent and non-patent matters in the courts.
Something similar to a registered patent agent profession exists in tax practice before the IRS. An enrolled agent can litigate in IRS administrative proceedings and tax court without actually being admitted to the practice of law.
Thus, the IRS and the U.S. Patent and Trademark Office both allow someone to be admitted solely to practice before those agencies without being lawyers in a state bar as a prerequisite. But, there is no such thing as "national" admission to the practice of law, in general, in the U.S.
Working As A Federal Government Lawyer Without A State Bar Admission
In theory, the United States government can hire and use as a lawyer someone who is not admitted to any state or D.C. bar association, for example, in the Department of Justice, or the White House Office, or the JAG Corps, because the supremacy clause allows someone engaged in an exclusively federal practice for the federal government to be immune from state bar regulation.
This is very rare in practice, but is important when evaluating state bar associations as a way to regulate federal lawyers in a systemic campaign to do so contrary to the wishes of a current Presidential administration.
For example, if a state bar disbarred an attorney working for the federal government, for example, for discriminating against LGBQT people because that is what the administration told the attorney to do, the federal government could continue to use that lawyer even though the lawyer was no longer admitted to practice in any U.S. state or in D.C., and the federal courts would probably not reciprocally disbar the lawyer in the federal courts if a case was made not to do so in that kind of situation. The federal court ultimately get to decide who can practice law before them, but usually defers to the federal governments requests on these matters.
Also, not every legal job in the federal government formally required a license to practice law as part of the job description (most notably, federal judges, certain White House advisers, and also some court-martial officials).
Additional Regulation Of Federal Government Lawyers
Federal government lawyers are also subject to certain kinds of federal government regulation that doesn't apply to other lawyers (e.g. they must defer to the U.S. AG's declarations regarding how the law should be interpreted in the absence of contrary guidance from a court).
In this scene from The Client Susan Sarandon threatens to sue Tommy
Lee Jones, who I understand acts as a Prosecutor, in front of the
State Bar
Would something like that be possible in common-law jurisdictions?
Basically.
The Grievance Process
Anyone can grieve a lawyer if they have personal knowledge of a violation of professional ethics by that lawyer. It isn't terribly uncommon for an opposing counsel to grieve the other side's lawyer if the opposing counsel appears to violate professional ethics although such grievances receive a higher level of scrutiny and skepticism.
Sue isn't really the right word. Someone files a complaint or grievance with the body that regulates the practice of law in the relevant state, and then public officials (sometimes volunteer lawyers) investigate the case and if necessary go through the quasi-criminal administration law hearings (without a jury in the usual sense although sometimes a committee or panel hears the case) necessary to impose professional discipline on the lawyer.
Often, the state supreme court has ultimately authority to review these decision on an appellate basis. Sometimes attorney discipline cases are in the original jurisdiction of the state supreme court but handled by a magistrate or special master before a final decision by it.
Grounds For Grievances Of Prosecutors
The more common grounds upon which a prosecutor can be grieved include a failure to disclose exculpatory evidence to the defense, serious criminal convictions in private life, and undisclosed conflicts of interest (e.g. having an undisclosed affair with the trial judge before who the prosecutor practices, or with a criminal defense attorney in the same case).
Possible Consequences Of Professional Discipline
Professional discipline can range from a private reprimand or agreement to take continuing education classes or seek substance abuse treatment, to a public reprimand, to suspension from the practice of law for a period of time, to disbarment, depending upon the severity of the offense under the facts and circumstances of the case.
Reciprocal Discipline
Professional discipline must usually be reported to every other jurisdiction to which the lawyer is admitted to practice, and usually, the other jurisdiction will impose "reciprocal discipline" identical to and concurrent with the primary jurisdiction imposing the discipline in the case of a suspension from practice or disbarment.