The website Executed Today has a post about the collapse of Papal rule in Avignon and the Comtat Venaissan in 1790, which was followed by a plebiscite, under French auspices, the following year which led to union with revolutionary France. The Holy See did not accept the loss of these territories until the Treaty of Vienna in 1814. There are articles online from Jstor about the end of the territory which may repay reading if you have access.
There is a short history of the Papal enclave at Comtat Venaissin
Avignon and the Comtat Venaissan
Charles Souvay in “The French Papal States during the Revolution” (The Catholic Historical Review, January 1923) describes the violent reunion to the French nation of the Papal States enclave around Avignon where Popes had formerly reigned. This June 11 lynching was as nothing for mob violence compared to the Massacres of La Glacière later in 1790.
In 1789 the French Papal possessions included the two Counties respectively called in Roman Chancery style the Comitatus Avennicinus, or High County, the principal city of which was Carpentras, and the Comitatus Avenionensis, or Low County, named after its capital Avignon; both together having in all an area of less than a thousand square miles. Since 1274, by donation of King Philip III to Pope Gregory X, they belonged to the Popes; and even though several times (1663, 1688 and 1768) the French kings attempted to wrest them from their legitimate sovereign, there was, in 1789, no question of disputing the Papacy’s rights. A Legate administered the two Counties, continuing in the old Papal Castle the moral presence of the popes who had resided there from 1309 to 1378.
The Counties were comparatively an earthly paradise: taxes insignificant; no imposts; living wonderfully cheap — “for one or two sous one could hve a meal of bread, meat and wine”; no militia, scarcely any privileges of nobility; no restrictions on fishing and hunting and to cap it all a miniature representative Assembly. However, the rank and file of the population had a bad name, and it deserved it. In the course of time the country had become the secure haven of all the scoundrels of France, Italy and Genoa: smugglers, fences, vagabonds, swindlers, crooks, convicts escaped from the galleys of Toulon and Marseilles, all flocked there and soon fraternized in debauchery and crime.
Such ingredients constituted a soil admirably adapted for the rapid growth of the revolutionary seed. No wonder, therefore, that towards the end of 1789 rebellion broke out in Avignon, where minds were easily wrought up. Before long it spread beyond the ramparts of the City of the Popes. The high County, however, remained loyal; hence timid: fear of the violence of the demagogues — a fear but too well founded — increased the numbers of the anti-papal faction; and soon the noise they raised was such that the Pope had to intervene. He did it in a fatherly way, promised all the reforms deemed opportune (Briefs of February and April 1790) and sent a Commissary with the charge of trying every possible way to restore order and peace. At Carpentras the pontifical Commissary was shown he was unwelcome; at Avignon he was positively refused admittance.
Then in the papal city Jacobinism, preached by ranting advocates like Tournal, Rovere, the two Duprats, the two Mainvielles, Lecuyer, multiplied its proselytes and stopped at no violence. Within a short while seven or eight riots broke out. On June 10, 1790, at the instigation of the leaders, all the rabble of the city and the suburbs, churls adverse to excise, rapscallions adverse to order, stevedores and longshoremen, armed with scythes, pikes and cudgels, rose up tumultuously, served on the Vice-Legate Casoni notice to quit, turned out of the city the Archbishop Giovio, ousted the Italian officials, obliged the Consuls to resign, hanged the officers of the National Guard and the principal loyalists (June 11)* and possessed themselves of the town hall. For efficiency trust the preachers of the revolutionary gospel.
* Seven men were murdered that day; some were nobles, others priests and others artisans.
Personally I think the world was more interesting and, frankly, more fun when there were such sovereign or autonomous territorial units - today there are but a few left in Europe.
The flag of the Comtat VenaissanIt is interesting looking on the Internet to see that flags and items such as cuff links bearing the arms of the Comtat are available for sale.