This Tontine wikipedia article says,
Financial inventions were patentable under French law from January 1791 until September 1792
Why did that practice stop after less than 2 years?
The late 1780's were a time of economic struggles for the French. In particular, the Monarchy was consuming funds at a simply unsustainable rate, with a personal guard of almost 10,000 soldiers and a civilian household of 4,000. Keep in mind that France had around 25 million people at the time, meaning that 1 in every 1800 people in the kingdom worked directly for the king. By comparison, that would be like 180,000 people between White House and Secret Service staff for the US. This extravagance is one of the factors that pushed the Parisian public over the edge to revolution, boiling over on July 14, 1789 with the storming of the Bastille, and shortly thereafter, Louis became a constitutional monarch.
However, transitioning much of the power from the monarchy to parliament doesn't automatically get the economy rolling again. In March 1790, the new National Assembly voted to institute a paper currency planning to put in 400 million units of currency. A few short months later circulation had tripled. The new government was going to need to find a way to jump start the economy. Or failing in that, they at least needed to raise funds to have a government at all, especially while the king was still alive. Otherwise, there was a chance he could simply consolidate power again and show the people "Look you thought the problem was me, but you tried them and it didn't work. Try me again, and I'll cut down on the extravagance." Or something. Kings are wily like that.
So, they turned to the French public. If you can come up with some kind of financial scheme that allows the government to raise the necessary funds, you'll be able to patent it. Now the tontine specifically was already in use for decades before in France (ironically, by King Louis to finance his military) and you would think that means prior art so thoroughly established would make this particular invention unpatentable. But you'd be wrong, because clearly someone did it.
September 1792 was a rough month for the French Monarchy. As the past few years had seen the King imprisoned, this was no longer enough for the National Assembly, so they eliminated the position of King (and later gave him the traditional haircut.) They also disbanded the Assembly, as the assembly existed to oversee government as a constitutional monarchy, and with the National Convention having opened in August 1792, there was no more need for the assembly.
The convention, it would seem, did not directly recognize the patentability of financial inventions. I guess if you invent a financial scheme, you'll just have to use it to get rich instead of license it.
The French Assemblée nationale législative saw financial patents as 'dangerous' as they were open to abuse and could be used to exploit people. The issue of speculation was a major concern at the time, and the fear was that financial methods patents would encourage this.
Thus, on the 20th of September 1792, following a debate, the assembly voted to abolish patents for financial methods. Other exclusions were also made in further revisions (theoretical or scientific discoveries without practical application, medicines).
The issuing of patents and privileges had for long been in the hands of the king, and open to abuse and favouritism. Thus,
The Revolutionary Assembly intended to avoid the excesses involved in previous grants of privileges, and proclaimed that it had drafted the outlines of a system that created a distinct break with the past.
Of primary importance in the bringing of the proposal for new patent laws to the attention of the
Comité d'agriculture et du commerce was the Société des inventions et des découvertes. They demanded a new patent law:
Stanislas de Boufflers was nominated as a rapporteur. He presented his Rapport sur la propriété des auteurs de nouvelles découvertes et inventions en tout genre d'industrie on December 30, 1790. Boufflers was clearly inspired by Diderot's arguments, pointing out that « if there is a genuine property to a man, it is his thought. » For him, the inventions were considered as inventor's products, which property has to be secured.
Source: Gabriel Galvez-Behar, Patents and the market for technology in the early 19th century France
The first patents (renamed 'brevets d'invention' in French) law of 7 January 1791 was all-encompassing in its guidelines as to what the law applied to.
was immediately contested by those, who considered that patents were useless privileges
Source: Gabriel Galvez-Behar
but determined lobbying by the Société des inventions et des découvertes ensured that the first law was backed up by a second law in May 1791.
The evidence suggests that the main motives for the new patents law were to end the abuses of the previous system and to protect inventors, in part so that France would benefit from their ideas becoming public; note that inventors who applied for patents in other countries would be 'punished' by losing their French patent.
The initial impact of the law was minimal in terms of the number of patents (or 'brevets d'invention' as they were now called) granted - there was initially (until 1824 onwards) no increase in the number granted. Financially, the state benefited very little (if at all); obtaining a brevet d'invention was very expensive, one reason why there were so few applications.
Nonetheless, brevets d'invention for financial methods raised concerns; financial speculation was a major issue at the time, especially in relation to the government-issued assignats (a kind of paper money supposedly secured by assets and land confiscated from the church and the nobility) which, largely due to over-issuing, were decreasing in value, thereby creating unrest and undermining the government's efforts to raise money. As financial speculation tends to concentrate money in the hands of a few, it is hardly surprising that the more revolutionary elements of the government were looking for ways to discourage it, even if the issuing of financial patents was not a significant factor with regards to assignats.
Revisions were proposed in 1792. The Archives Parlementaires for 20 September 1792 has a summary of the debate on financial patents. The motion to abolish them was proposed by M. Raignoux and supported by M. Jollivet.
M. Raignoux demande la revocation des brevets d’invention en matière de finances, qu’il a présentés comme une source d’agiotage...; que les brevets d’invention qui pourrait être delivrés pour des établissements de finances deviendraient dangereux;
M. Jollivet appuie la proposition en montrant, comme M. Raignoux que ces brevets serve qu’a tromper le people, en legalisant l’agiotage.
Mr. Raignoux asks for the revocation of patents of invention in matters of finances, which he presented as a source of agiotage ...; that patents that could be issued for financial institutions would become dangerous
Mr. Jollivet supports the proposal by showing, as Mr. Raignoux, that by legalizing agiotage, these patents only serve to deceive the people.
(Agiotage is the speculative buying or selling of stocks)
Despite some opposition, the motion was passed and Jean-Marie Roland de la Platiere, who was Minister of the Interior, abolished them the same month. At the same time, the 14 patents for financial methods which had already been issued were revoked.
Augustin-Charles Renouard, Traité des brevets d'invention de perfectionnement et d'importation