Because, apparently, US law should apply everywhere.
Radley Balko says: "I have a piece up at Huffington Post looking at a new House bill that would make it a federal crime to plan or advise any activity in another country that would violate U.S. drug laws, even the activity is legal in the county where it's planned to happen. The law would make it a crime, for example, to plan a trip to Amsterdam for the purpose of smoking pot, or to advise someone in another country how to grow medical marijuana (even if medical pot is legal there)."
The House Judiciary Committee passed a bill yesterday 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 (CSA) -- even if the planned activities are legal in the countries where they're carried out. The new law, sponsored by Judiciary Committee Chairman Rep. Lamar Smith (R-Texas) allows prosecutors to bring conspiracy charges against anyone who discusses, plans or advises someone else to engage in any activity that violates the CSA, the massive federal law that prohibits drugs like marijuana and strictly regulates prescription medication.
The bill has only passed the House Committee so far. It seems like it wouldn't become law.. or would it?
It wouldn't be the first time. Over the last several years, a number of executives from online gambling companies have been arrested in U.S. airports and charged with felony violations of U.S. gambling, racketeering and money laundering laws, even though the executives were citizens of and the companies were incorporated in countries where online gambling is legal.
The whole world is subject to US law, just don't actually come to the US. We probably won't let you in.