Here is a link to a short post on the Legal Ethics Forum discussing a bill recently approved by the House Judiciary Committee that would make it a federal crime for U.S. residents to discuss or plan activities on foreign soil that, if carried out in the U.S., would violate the Controlled Substances Act -- even if the planned activities are legal in the countries where they're carried out.
Suppose a client says to a lawyer, "I'm traveling to Amsterdam and would like to smoke some hash while I'm there. Is that lawful?" Would answering the question, and providing legal advice, constitute a crime?
Read the Legal Ethics Forum comment here which includes a link to an article in the Huffington Post discussing the issue in more detail.