Can anyone enlighten me if there are economic theories where labor is considered as a commodity like cloth and wine in the Ricardo theory, so that it can be exported and imported similarly to other commodities? I would be grateful for references.
So in modern English, a commodity is a raw material for production or basic agricultural good that can be exchanged for money. Labor, by this definition, is neither a raw material, no one grinds humans up to build stuff, I hope; an agricultural good, similar reasoning; nor exchangeable for money, as slavery and indentured servitude is illegal and efficient in most places. (Letting people make their own work decisions, or at least not forcing them to work, is good, generally speaking.)
Even with a more generously wide definition of a commodity, commodities are generally seen to be fungible, which means you cannot easily differentiate between the good/service based on region, or that they all of each type of commodity is seen as equivalent. So if you are willing to say that all labor is equivalent...
Basically, labor is generally not seen as a commodity.
I cannot comment because of too little reputation. So please note that this response is an extension to the response of Giorgio stating that Marx abstracted labour to a commodity in Das Kapital.
With regards to import and export I don't think you have to go as far as talking about slavery. On a more local scale labour is continuously imported and exported. Companies are recruiting on university campuses. The people there come from different locations. Maybe they are from a town in the east of the country and they will go for a job in the west of the country or the other way around. In a way the labour that could have been put to use in the one part was exported or imported, depending of the point of view, to the other part of the country.
Now lets try to up the scale. Instead of looking at one country lets look at the world. The following example is not 100% historically correct, but bare with me and try to see the concept without getting stuck on historical details or moral principles. It's about the mechanics of the economics.
Decades ago we found coal in Belgium. We needed people to work in the mines. The investors wanted to get the mines up and running. This caused a spike in the demand for young able people whom were not afraid of danger. There weren't enough people, so we recruited a labour force in Spain, Italia, Greece and Turkey. In a manner of speaking you could say that Belgium at that point imported labour. Off course you don't use people as you would other commodities. There are sociological/social consequences to these kinds of actions. Those I won't touch because they are out of scope of this question.
With a little imagination you could also see a huge export of labour these days. Refugees are people who want to live. They move, and they need jobs. You don't even need actual refugees. In Europe the united market made it possible for people to work all across Europe. That causes an influx of labour force. Populists very much like to say they 'steal' our jobs. In a way they say that these influxes of labour, or excessive exports if you like, flood our market for labour like china stereotypically floods the market with cheap plastic stuff.
To conclude - If you choose to study mechanics of import and export, and you choose to abstract labour to a commodity as proposed in Das Kapital, then you could definitely apply analogous principles to labour with regards to import and export as you would for other commodities.
Under the broader definition of commodity (due to Marx, Das Kapital, Volume 1, Chapter 1, Section 1) as some material or immaterial thing that satisfies some human need, that can be owned, bought and sold on the market, labour power can be seen as a commodity:
- It can produce useful things or services
- It is owned by anybody who is able to work
- It can be sold on the market for money
More precisely, labour power is sold as a commodity since its owner (the worker) sells it for a certain amount of hours to a buyer (the employer) according to a contract. The buyer owns and has the right to use this commodity for the number of hours it has been purchased by letting the seller perform work under his command. The buyer also owns the product of the purchased labour, and can use it or sell it on the market.
In a production process, labour power is treated as an input commodity like any other (raw materials, machinery, and so on).
Regarding import and export I am not sure. Since it is not the worker that is bought (this would mean slavery) but his / her labour power for a certain number of hours of the day, it is not very practical to import / export labour power. However, I think there exist companies that subcontract workers so that they can work abroad for a period of time. Maybe this can be considered as import / export of the labour commodity.