Stan, you are correct in that there is a body of federal case law that holds that if a debt collector brings legal action on a knowingly time-barred debt (i.e., they have actual knowledge that SOL has expired), it is a violation of the FDCPA.
The debt is still owed, and expiration of SOL does not negate that fact... they just cant go use the courts as part of their collection practices if the are clearly aware that the SOL has expired. I would be careful, however, in general application of that case law, as it presumes actual knowledge. It is often not possible for a debt collector to be aware of actual expiration of SOL, such as if a state code includes reset provisions of which they have no knowledge.
For the most part, assume they can bring legal action, and you will still have to raise an SOL defense unless you have evidence of actual knowledge on their part.
