Has this ever been done?
It was done in the Reconstruction period in the American South, as explained in a recent Congressional Research Service report on the question. As it explains:
Congress could also enact new legislation to enforce Section 3 in the
aftermath of January 6, much like it did in response to the Civil War.
Congress initially provided enforcement of Section 3 of the Fourteenth
Amendment through enactment of the First Ku Klux Clan Act in 1870.
Section 14 of that Act directed the district attorney in each district
in which a potentially disqualified person held office to file a writ
of quo warranto against the office-holder before a judge. Section 15
of the Act made it a misdemeanor for a person disqualified under the
Fourteenth Amendment to hold state or federal office, enforcement of
which required a court conviction.
However, after two years, Congress reversed course by providing
amnesty from the disqualification under the First Ku Klux Klan Act
through enactment of the Amnesty Act in 1872. . . . The Ku Klux Klan
Act provisions no longer appear in the U.S. Code, and Congress has
not since exercised its authority under Section 5 of the Fourteenth
Amendment to enact legislation providing a general procedure for the
executive and judicial branches to determine who is subject to the bar
on holding office.
Thus, both a civil lawsuit, and a criminal prosecution were available to remove someone from office even if they had not been convicted of an insurrection related crime.
If so, how can a civil disability be applied to an individual without
first holding a trial?
Due process would require an opportunity to review the determination in a process which provided a right to present evidence and be represented by an attorney, for example, which is ultimately reviewable by a court.
Under the Ku Klux Klan Act of 1870, this was done by having a district attorney bring a lawsuit to remove someone who was within the Amendment XIV, Section 3 exclusion after they were elected, if necessary. But, that isn't the only conceivable procedural approach.
But, it isn't obvious that you couldn't have a process in which the determination were made first, administratively, and could be contested within a reasonable time after the person affected has notice of it by having the affected person bring a lawsuit challenging the determination.
The process would have to have a timeline that would not prevent a person who successfully challenged the classification from running for and winning public office. So, for example, it couldn't be done shortly before an election is held.
The CRS Report continues by examining some of the other current legislative options:
In contrast to general procedural legislation akin to the Ku Klux Klan
Act, there is some debate as to whether Congress can enact a law
naming specific individuals subject to disqualification. As is
discussed in another Legal Sidebar, some argue that Congress has that
right under Section 3, while others counter that such a measure might
conflict with the constitutional prohibition on Bills of Attainder.
The Supreme Court has described a bill of attainder as “a law that
legislatively determines guilt and inflicts punishment upon an
identifiable individual without provision of the protections of a
judicial trial.” It is unclear whether legislation to implement
Section 3 is subject to the constitutional prohibition on bills of
attainder or was instead intended as a constitutional exception to it.
Whether disqualification from holding office constitutes punishment
for the purposes of the Bill of Attainder Clause is also unclear. Due
to these uncertainties, legislation that specifically identifies
individuals for disqualification would likely result in litigation.
Article I, § 5 of the Constitution provides the House and Senate with
near complete control over their own membership through the distinct
constitutional powers of exclusion and expulsion. Either of these
powers could be used to enforce a disqualification under the
Fourteenth Amendment, at least with respect to an individual’s ability
to serve in Congress.
An exclusion occurs when either the House or Senate refuses to seat a
Member-elect. That power derives from the Constitution’s charge that
“Each House shall be the Judge of the Elections, Returns and
Qualifications of its own Members. . .” and may be achieved by the
vote of a simple majority.
An expulsion, on the other hand, occurs when either chamber removes
one of its current Members. That power derives from the Constitution’s
explicit statement that “Each House may . . . with the Concurrence of
two thirds, expel a Member.” As reflected in the provision, an
expulsion requires the consent of twothirds of the chamber.
The power to expel is much broader in scope than the power to exclude.
Both chambers have “almost unbridled discretion” to determine the type
of misconduct that warrants expulsion. The Supreme Court has
suggested, for example, that Congress’s expulsion power “extends to
all cases where the offence is such as in the judgment of the Senate
is inconsistent with the trust and duty of a member.” Grounds for
exclusion, however, are limited to those enumerated in the
Constitution. In Powell v. McCormack, the Court established that
“the Constitution leaves the [House and Senate] without authority to
exclude any person, duly elected by his constituents, who meets all
the requirements for membership expressly prescribed in the
Constitution.” As shown in the Berger experience discussed above,
Congress has previously viewed Section 3 of the Fourteenth Amendment
as establishing an enumerated constitutional qualification for holding
office, and, consequently, a grounds for possible exclusion.
