Although it may sound paradoxical, stories about inherent autism of the current authorities do not make sense in this case. In the situation where the state blocks its own export and gives up even the existing, although minimal, foreign currency inflow, the Serbian currency is suffering from very strong pressures: black market exchange rate has reached 30 Dinars for one German Mark, which threatens to cause large disturbances on the domestic illegal (since there is no legal) currency market, after which an increase in inflation would be unavoidable. For a country which "prides" itself on stability of prices and exchange rates, such a move is far from being rational.
However, exactly with this goal in mind, in order to preserve the mentioned "stability of prices and exchange rates" Serbia was forced to block the borders. Since, the domestic control of prices has caused a flight of goods from stores, and traders would now gladly export their surplus, crated by state policy, and make profit instead of losses. And that is the key reason for a ban on exports. Permits for increase in prices will not be issued gladly, at least until the next elections, and no rational producer would accept to sell his goods at a significant loss. Even in state-owned companies the motivation will be the same, and the eventual amounts of milk, cooking oil etc. appearing on our domestic market will be the result of political pressures, negotiations and so on. Nevertheless, it seems that monthly reports about the true inflation rate are still the main priority of the Serbian economic policy.
But, why are the authorities then blocking the imports of everything apart from iron and aluminum? Exactly because Montenegro does not have another buyer for these products, and sells them at very low prices, which won't influence the Serbian inflation rate. Other products, especially consumer goods, could be sold at the prices determined by the importer, which would in the near future definitely put pressure on the inflation rate. Therefore, the basic suspicion is that the citizens would drink Slovenian or Hungarian milk and maybe even prefer their or somebody else's cooking oil or sugar, as long as they can buy them. And, again, that would disturb the policy of "the stability of prices and exchange rates".
When such a perverse goal is set as the main goal of an economic policy all other moves are forced, among other the above mentioned export-import blockade. Therefore, this move is not an ideological move, nor is it motivated by foreign policy, but simply there is no other way to minimize the growth of prices within the country.
The remaining question is whether this, obviously rational move by the state, will succeed. It won't! And the economic theory has been aware of that since the Roman Empire. Since at the time judiciary was somewhat more cruel than today, it is worth mentioning that in year 301 B.C. emperor Diocletian introduced death penalty for all those who sell or buy goods at prices higher than those prescribed by the state. His only achievement was that traders tried to move their goods outside Rome and export them. At the same time (what similarity!) the state became the largest trader within the Empire and managed to suppress many small-scale traders and force them into bankruptcy.
In the end, I quote the words of Professor Gojko Grdic written in 1941 regarding the economic reasons for the downfall of ancient Rome: "All of these were signs of primitivism, towards which the economy of late antiquity was hurtling without brakes. That practice was maintained in the Byzantium well into the late medieval period." Therefore, it failed, lasted for a long time, and a millennium later, some others are still trying the same recipe...
The author is a member of the Center for Liberal-Democratic studies