How would it legally work?
For example, could India force U.S. consulates to stop issuing H-1B visas, or other specialized visas, by claiming it amounts to poaching of important human resources?
Edit: I used 'brain drain' as just an example. What I wished to know was how much control can a country exert on other countries' consulates on its land. Barring shutting down a consulate, what can a country do to prevent issuance of visas?
I assume the goal here is for nation A to prevent citizen A1 from travelling/emigrating to nation B.
It can be done, but not in the way you're suggesting. It can be achieved by instituting exit visas.
Nepal requires citizens emigrating to the United States on an H-1B visa to present an exit permit issued by the Ministry of Labour. This document is called a work permit and needs to be presented to immigration to leave the country.
Which is essentially what you're after, if I understand your question correctly.
In short, nation A cannot tell nation B to not grant a particular visa. But nation A can require citizen A1 to get nation A's explicit permission to travel to nation B.
However, as you can see in the list of examples on the Wikipedia page, exit visas are not all that common and are often linked to fascist or authoritarian regimes (which means that imposing an exit visa is liably going to raise a few eyebrows in western society, to say the least).
I was genuinely surprised that Nepal still has an exit visa; I initially wrote my answer under the assumption that I would only find historical occurrences.
In general there is no legal mechanism for this to happen unless the two countries sign a treaty to create such a mechanism. Countries might be able to use political or diplomatic pressure to achieve this, but that is out of scope for this site.
One thing countries can do through their legal systems is to place restrictions on their own citizens. So in your example, India could make it illegal for its citizens to take H-1B visas in the US, or it could place other less absolute restrictions. In fact, India has already done something like this for workers going to certain countries with the "emigration check required" passport. The US is not among the covered countries, however.
Seriously. Several answers mention this, but it deserves so much more than a mention. You don't stop nation B (and the 193 others) from issuing visas, you stop your own citizens from leaving without approval.
If you remember the pre-perestroika Soviet Union (now over 30 years gone), you feel the chill in your bones. Such a scheme is an affront to human rights. With ancient European countries today having nothing but a sign at their borders, it's easy to forget some countries were building walls to keep their citizens in.
That is the traditional way to deal with brain-drain. But there's another.
Even if your home country doesn't have exit controls, the passport is their property. And most countries have a law that if they issued you a passport, you must enter the country on that passport. That means they will see the stamps in it. Even in a freer country like the US there can be consequences for, say, a person who's a weapon designer by trade making a trip via Netherlands and Russia to North Korea and having apparently spent a year there.
Country B can conspire with the visitor to conceal their visit; but this leaves holes in their passport: how did our designer spend a year in Russia without a Russian visa allowing a long stay?
So the Nepalese who slips into India to depart to the US still may face consequences when they return home.
Ah, but can't they file for asylum with country B, because of these oh-so-unfair consequences? Only if the consequences are extreme. A tax or fine certainly would not qualify (for instance the United States endorses, in the sincerest way, your home country taxing your foreign income!) Nor would a modest amount of jail time in a halfway respectable jail.
There is no* effective way to do so, unless procedures by B in some way assist A (e.g. by stamping passports, or sharing travel records).
There are exit visas, as Flater points out, and similarly a country A can prohibit direct flights from its airports to country B. Both of these can and will be trivially worked around by travelling to country C first.
*There are some ways, but they probably aren't what you're looking for:
A passport is a document by which a nation (in this case A) effectively grants permission to travel to its subject A1. Without a passport, other countries will generally not let A1 enter. One reason is that without a passport, country B will not be able to deport A1 back to A. The passport guarantees that A will take A1 back, this is a reason that often passports need to be valid for several months past the end date of the visa. This is to give B enough time to deport A1. If A agrees to accept expired passports for re-entry, then B might relax this validity requirement.
This opens another possibility to restrict travel: make the passport invalid for travel to country B. Most passport have the following text "Valid to all countries" written in many languages in the front. Country A could put in "Not valid for country B". While technically country B could decide to ignore this note and could even issue a travel document for A1 (there are passports for non-citizens, called 1951 Convention travel documents), this is quite unlikely and typically only happens for recognized refugees.
One example of a limited passport is Pakistan, which looks like this:
Of course, the choice is up to Israel to let anyone in, but I doubt it would make travel easier.
Another option for A would be to make the passport not acceptable to country B. For example, the US. requires machine readable and biometric passports for travel under the Visa Waiver Program. If country A gives handwritten passports to its problem citizens, they will need to get a visa. Also, ICAO phased out handwritten passports in 2015, so non machine-readable passports are now useless for air travel. Realistically though, country A could keep its population more easily captive by not issuing passports or requiring extra permits.
Another example is be Saudi Arabia, where women cannot get a passport without permission of their 'guardian', they also have an electronic authorization system where the guardians need to authorize travel.
In 2017, the US. passed a Megan's law adding the following text to passports of certain sex offenders:
I am sure many countries will not issue a visa to a holder of such a passport. The US. generally denies entry to people convicted of crimes of moral turpitude. Canada required George W. Bush to get a special permit because he was convicted of a DUI.
Country A cannot prevent Country B from issuing visas to citizens of Country A.
The right to issue visas is sovereign to each nation's issuing authority.
As mentioned in other answers, any country can restrict exit from its borders. This is done usually through exit visas, but sometimes it can be achieved by instituting additional requirements of their citizens.
India, for example, has the Emigration Check Required (ECR) (Bureau of Immigration) rule, which states:
As per the Emigration Act, 1983, Emigration Check Required (ECR) categories of Indian passport holders, require to obtain "Emigration Clearance" from the office of Protector of Emigrants (POE), Ministry of Overseas Indian Affairs for going to following 18 countries.
United Arab Emirates (UAE), The Kingdom of Saudi Arabia (KSA), Qatar, Oman, Kuwait, Bahrain, Malaysia, Libya, Jordan, Yemen, Sudan, Afghanistan, Indonesia, Syria, Lebanon, Thailand, Iraq (emigration banned).
However , the Ministry of Overseas Indian Affairs (Emigration Policy Division) have allowed ECR passport holders traveling abroad for purposes others than employment to leave the country on production of valid passport, valid visa and return ticket at the immigration counters at international airports in India w.e.f. 1st October 2007.
If the RPO has issued Indian passport either with endorsement of “Emigration Check Required” or no endorsement of “Emigration Check Required” in the passport, POE clearance is required only when there is “Emigration Check Required” endorsement in the passport.
Kuwait issues restricted passports to its stateless residents which allow them travel on a case-by-case basis. The person has to surrender the passport upon return.
You may also be subject to additional scrutiny (or be arrested!) upon your return if you have violated the country's exit laws. This is most common in countries that still follow conscription.
Egypt has such rules, restricts exits (source: wikipedia) and does imprison defaulters if they happen to return within their obligation period.
Service is postponed for students until their studies are finished, before they turn 25 years old and they can not travel abroad without travel permit from the Ministry of Defense.
Check Article 13, 2 of The Universal Declaration of Human Rights:
- Everyone has the right to leave any country, including his own, and to return to his country.
Similarly, we find in Article 12, 2-3 of the International Covenant on Civil and Political Rights:
Everyone shall be free to leave any country, including his own.
The above-mentioned rights shall not be subject to any restrictions except those which are provided by law, are necessary to protect national security, public order (ordre public), public health or morals or the rights and freedoms of others, and are consistent with the other rights recognized in the present Covenant.
So in general, any country acceoting the basic human rights standards cannot do what you ask for. As long as we are taling about "normal" brain drain instead of top scienteists of the domestic nuclear program, I don't think they can pull the natinal security card, for example.
Then again, there is no way to force a country into following human rights: How many politicians travel to "evil" states with the "intention" to also mention human rights, and end up making business deals? And just recently, we observed a major western democracy may withdraw from inter-governmental bodies installed solely for the promotion and protection of all human rights around the globe.
Country A can categorically close its borders to its citizens exiting country A.
See "iron curtain" and the borders in question for most prominent example in recent history.
Country A can also issue exit permits or visas as a prerequisite for its citizens to leave country A.
One method might be to offer education costs, especially higher education costs, as a loan, forgiven over time, rather than as a highly subsidized benefit to citizenship or residency.
Depending on agreements between governments it may or may not be all that easy to collect on the loan, but at least the poachee could be deprived of expensive future benefits such as retirement income and medical care in their old age, or ability to own cheap real estate at home if they take all the benefits of citizenship and then leave.
India in particular apparently has a very effective method of inhibiting mobility domestically called a relieving letter.
