An advice of counsel defense can be effective.  If established, the defense shows that the defendant lacked the necessary criminal intent, or mens rea, to commit the crime.  The advice-of-counsel defense is only available if the alleged crime requires specific intent.  A large number of crimes require specific intent – e.g. obstruction of justice; fraud; false claims.  The defense has never been raised in an FCPA case, but there is no logical reason why it could not be raised. 
The advice-of-counsel defense is only available if the advice was sought before action was taken since the individual has to establish that he or she relied on the advice.  In practice, the advice of counsel should be sought whenever there is a grey area which can be resolved through legal advice.  In seeking such advice, it is important for the employee to disclose all relevant and material facts. 
It is important for companies to document and keep accurate records of requests for legal advice and responses to such requests, as well as the documents provided to counsel for review.  It will be much easier for a defendant sustain an advice of counsel defense if they made contemporaneous records indicating what documents were disclosed to attorneys, as compared to having to determine what was disclosed at a later date. In addition, contemporaneous records will have more credibility with a jury.
The advice of counsel defense does not come without risks and legal complications.  The advice-of-counsel defense waives the attorney-client privilege protecting communications between a client and their counsel. A defendant may not both use the advice-of-counsel defense as both a sword and a shield.  The question of the extent of such waiver is often litigated and a significant risk when relying on such a defense.  Courts are reluctant to extend the waiver of the privilege far beyond the specific question of the advice at issue in the case.   
In this risky enforcement environment, compliance programs have to integrate practical steps to ensure that advice of counsel can be raised as a possible defense.  Criminal cases are extremely hard to prove when there is evidence that the company believed that the legality of its actions was unclear, sought advice of counsel, and then relied on that advice before engaging in the alleged criminal conduct.