« on: December 31, 2013, 11:59:48 PM »
Well, your question has a lot of moving parts, but I'll try to address the main issues.
Let me start with a caveat: I'm just some guy on the internet, and this is just my opinion. I could be wrong about a lot of this stuff, and I don't know the specifics of your situation. Don't make important life decision based on what I (or anyone else here) says. Do the research yourself, contact the state bars, contact the law schools, and contact the employers. They can give you better information than anyone.
Working in the U.S.
If you plan to practice law in the U.S. you must become a member of the state bar for the state in which you intend to practice.
Most states will require an LL.B holder to complete a U.S. LL.M before they can apply to take the bar exam. A handful of states such as California and NY will allow LL.B holders to sit for the bar without an LL.M. An LL.M is two years, a J.D. is at least three. However, the J.D. is better preparation for the bar exam in my opinion, as evidenced by bar pass rates. (The pass rate for foreign degree holders here in CA is very low).
For many legal jobs, the obsession over law school rankings is greatly overstated. (You don't need a Harvard J.D. to write wills in Little Rock, for example). However, there are certain fields of law in which prestige matters greatly and international law is one of them. Most of the big firms and international organizations are well stocked with graduates of elite institutions, and will usually only hire the same. If you are serious about this field, you really need to consider this. An LL.M from Unknown State U probably isn't going to cut it when everyone at the office went to Yale and Stanford.
If you plan to work in the U.S., then I don't think a European LL.M is advisable. It will not qualify you to take the bar in most states, and will not prepare you for the bar in the few states that may admit you. A U.S. LL.M seems to make more sense.
Is taking the bar necessary to work in international law?
If practicing international law involves appearing in U.S. courts or giving legal advice, then yes, you must be licensed.
"International law" is a bit of a misnomer in my opinion, as there is very little truly international law. Typically, you are talking about countries which are signatories to trade agreements or treaties. The laws are applicable to those nations or entities. So, if the U.S. and Italy have an agreement as to how arbitration clauses in sale of goods contracts are to be handled, and your client is an American manufacturer doing business in Italy, then you are advising your client on American and Italian law and you are filing and arguing cases (probably) in an American federal court. Thus, you would need to be a licensed attorney.
Working at the U.N. or IGO
Depending on what specific work you do, I imagine that bar admission may or may not be required for this type of job. If you are filing cases in U.S. courts and dispensing legal advice, then yes. But if the job is more like a policy analysis/policy development position, then maybe not.
One thing to keep in mind when discussing organizations like the U.N. is the stiff international competition for these jobs. In the entire world, you're probably talking about a few thousand people (or maybe a few hundred!) whose job fits this description. People who get hired tend to have many years of legal and/or diplomatic experience, very impressive academic credentials (Harvard, Oxford, etc), and have worked their way up the ladder. Some are professional academics with numerous publications and others are internationally recognized judges. I don't think very many lawyers at the U.N. or the Hague are hired straight out of law school. Not trying to be negative, just something to consider.