What are the legal issues when submitting work to publishers? is there a risk of having my work stolen?
How can you protect yourself from this?
Is there an international "law" for this or is it country-specific?
I am not a lawyer. The observations below apply in the US, I don't know much about international copyright law outside the specific area of software copyrights.
Here in the US, if you wrote something, you own the copyright on it, period. All you need in order to assert that copyright is proof that you wrote something, and when. There are many ways to do this. I tend toward digital signatures but that's the geek in me. Some people mail themselves a copy of their manuscript in a tamper-evident envelope so that they have the dated postmark on it and can prove it existed on the day it was mailed (note: keep it unopened until you get to court, so the judge sees you open it). Some people give a copy to their lawyer to hold. Some people simply share the work with enough friends/family that they figure enough witnesses will crop up if someone claims to have created the work.
If you aren't already familiar with cryptographic signatures, and a group of people or trusted neutral party who will sign your manuscript, the tamper-proof envelope is probably your most reliable, cheapest bet.
If you live outside the US, US copyright law will work differently for you, depending on what treaties we have with your country.
If you don't trust a publisher not to steal your work, why do you trust them enough to do business with them in the first place?
What are the legal issues when submitting work to publishers?
Your work must be your work. Don't submit anything that someone else has written, not even if you just copied a few sentences. Even if you changed them. There are companies out there that can run automated checks on your work to see if they can find something in it that even remotely looks like someone else wrote it. If that happens, your reputation can be ruined before it even started.
is there a risk of having my work stolen?
Not really. Think about it from the thieves point of view. If you work is bad, it won't sell so it doesn't make sense to steal it. If it's good, and they make a fortune, you will surely sue to get your money. Chances are that you will make it in court.
Either way, if your work is incredibly good or bad, there is only a small chance that someone will steal it. Stop worrying, put your energy into making your work better.
How can you protect yourself from this?
If someone really sets his/her mind to ripping you off, then there is little you can do. The point is not to be paranoid. What are the realistic chances that someone will steal your work?
There is also another side of the coin: If a publisher is accused to steal, that is very bad for their reputation as well.
Is there an international "law" for this or is it country-specific?
There is no International law and you should be happy about that. Copyright is a tool to make publishers rich, not you.
In 1800 in Germany, there was no copyright. England, OTOH, had a very strict copyright. The net effect: Ten times more books were published in Germany, they were cheap and many authors could live from their work (high demand for books -> better bargaining power for authors).
In England, only a few authors could live from their work, books were very expensive (one quarter of your monthly income for a single book). Publishers set the prices, there were many authors but only a few books got ever published because they sold so bad because they were so expensive, etc.
Source: Wem nutzt das Urheberrecht?
[EDIT] If you need a cheap and reliable way to prove that something is your work, here is an idea: When you mail the work to someone, mail a registered copy to yourself. Do not open the envelope, don't tamper with it in any way.
If you need to go to court, you can present the letter there and have the court open it to prove that the work is yours.
@HedgeMage: Some flaws in your argument:
With copyright, authors have to sell their work to publishers. If there is no copyright, authors can switch publisher at any time. In the first case, the position of the publisher is stronger. They decide who and what gets published. In the latter case, the authors are in power.
Say all copies of your book have been printed and your current publisher doesn't want (for whatever reason) print more. Today, your work is lost. Even if you could have more readers, you won't. It's out of your control.
With copyright, no one can publish your work against your will. So you can create an artificial demand, which drives prices up. But only for those who are in demand. If anyone can print any book, authors can't sit back. They have to write more and more books. So that's better for the readers: Fewer books will go out of print.
Now you'll argue that authors won't get any money if anyone can pirate their work any time.
How so? If a book isn't published at all, no one can pirate it. So only published books can be pirated. When a book is published, you need to make a copy of it (scanning, proof-reading, etc). So pirating isn't free, it costs money, too. And time. Eager fans will buy the book as soon as possible, so the author will always get money from the first time publisher. But since there is no copyright, the author can have their book printed by a second publisher, too - and get money from two sources.
If a publisher doesn't want to ask for permission, well, you can't force them. There is nothing preventing them to print any book. But there must be a market, too. So their copy must have some unique value to the readers. Maybe its much cheaper.
As an author that gets me thinking: "If my current publisher is so expensive, that means fewer people buy my books and I could get more per copy if that other publisher printed it ..." Not something your publisher will want to hear, I'm sure.
If your publisher offers you better service than the "cheap pirate", you can still stay. But now, it's a decision, not something forced by the law. It will hurt your feelings if someone makes a lot of money with a re-print but fact is that this money could have been yours if you had the guts to pick it up. You don't want to take the risk? Then on what grounds do you demand a share?
I'm not saying that there won't be problems, I'm saying is that as the author of my work, I get more say in the matter.
The article linked about gives a lot more reasons why copyright is basically a well sold lie. Yes, it makes a select few very rich (first of all the publishers and then a few best-seller authors) but I'm pretty sure even Mrs. Rowling would agree: It would be better if a million authors more could live from their work rather than she make a few billions more.
One method I heard of to protect yourself is to mail yourself a copy of your work before you submit it. That way you can have a sealed and postmarked copy of your work in case of plagiarism. I am not sure if this also applies to digital media but archiving a copy of any emails sent out containing your work might be a good idea.
In the U.S. and other Berne Convention signatories, you own the copyright in a creative work as soon as it is fixed in a tangible form (e.g., a computer file). You do not need to register to have a valid copyright. However, you do need to register before you can file suit against someone for copyright infringement. You do not need to have registered before the infringement occurred, but if you did not, your claim is limited to your actual damages.
Registration is considered prima facie evidence that you own the copyright, which means that the court will consider you the owner of the work unless compelling evidence to the contrary is offered.
BTW, mailing yourself a copy of your manuscript does not hold up in court because it does not provide evidence of authorship of the work, merely of its existence at a particular time, and not even strong evidence of that (since you can mail unsealed envelopes, steam them open and reseal them, etc.).
While an answer has already been selected, I wanted to add some further points. In the US, you must have registered your copyright to begin an infringement lawsuit. You can register your copyright either before or after the date of infringement. However, registering copyright before an infringement provides for additional benefits not available when filing after the infringement. This affects what must be proved and the amount that can be awarded. For more information, read this Advantages of Copyright Registration article at publaw.
I am not a lawyer, my post comes from my experience working in the publishing world. It's also only what I know of the US copyright laws, not any international ones.
Purchasing a copyright isn't required. You own the copyright to your work, no matter what. The "poor man's copyright" (mailing yourself a seal copy of the manuscript) is no longer a valid way to prove copyright. If the manuscript in question is published, the contract you sign with your publisher is all the proof you need to prove that it's your intellectual property.
If you decide not to register your copyright with the US Copyright Office, you can't recover court costs. You can recover damages for the actual violation, but not any legal fees incurred pursuing the case. (Meaning lawyer fees, general court costs, etc.)
I did a little research on UK copyright, and there is a small amount of information at the UK Intellectual Property Office website.
It recommends sending a copy by post (special delivery) and leaving it unopened to prove the date it was in your possession. Whilst this does not prove you created it, or own it, it does prove that you had the work in your possession at a fixed date and time, which when use in court will help prove your ownership. It also suggests sending it to a solicitor or lawyer or bank, but this will cost money, and does not add any extra evidence (apart from it maybe more securely held, and less likely to be lost!)
I post a copyright notice on things I publish/blog on the Internet. IANAL, but AFAIK, it's copyrighted when you write it and release it.
Proving that is something else. Ultimately it would be a judgment call in court. did you write it first, and can you prove it.
If you are really worried, get a lawyer and use them to hold copies of your work with some type of signature/affadavit on the vessel storing the work, or even use a safe-deposit box and do the same thing, with recorded dates of entry.
Copyright laws tend to be similar everywhere, because most countries adhere to the Berne Convention. Details may vary, and of course enforcement can also between countries.