There's no reason a lawyer in India couldn't learn US law. He probably wouldn't even start very far behind US citizen. The real problem is that he can't set foot in a US courtroom without a visa.
random google survey:
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Here's a list last updated in 2008: http://www.prismlegal.com/index.php?option=content&task=...
To me, this is indication that there's a flood being held back by legislation.
You might be able to do that remotely - but it would be pretty difficult to do some things (e.g. how do you attend court?).