united-states
Marketplace faciliating the sales of goods not allowed across state lines
<p>Lets say Bob develops an online marketplace that helps facilitate the sale between widget makers and widget buyers. In some states, widgets are illegal. It is also currently illegal to sell widgets across state lines. But Bob isn't directly selling the widgets. His marketplace simply facilitates the pairing of widget makers and widget buyers and takes a small fee for the transaction and acts like an escrow for the sale. Bob knows this might be a problem for a US based company. So he opens the company in Costa Rica (This is an arbitrary choice, Any other country just not in the US) and hosts the marketplace outside of U.S. territory. Furthermore, his T.O.S state that in countries with laws against widgets. It is the Buyers &amp; Sellers responsibility to adhere to their countries laws.</p>

<ul>
<li>Can Bob be held liable for the sale of widget's across state lines?</li>
<li>What if the Buyer &amp; Seller are both in states in which widgets are legal?</li>
<li>What if the Seller is in a legal widget state but the Buyer is not?</li>
<li>What happens if the marketplace was built for zero knowledge transactions? (The site owner doesn't know about specifics of the transactions)</li>
</ul>

<p>Bob would be criminally liable, under <a href="https://www.law.cornell.edu/uscode/text/18/2" rel="nofollow noreferrer">18 USC 2</a>:</p>

<blockquote>
  <p>(a) Whoever commits an offense against the United States or aids,
  abets, counsels, commands, induces or procures its commission, is
  punishable as a principal.</p>
  
  <p>(b) Whoever willfully causes an act to be done which if directly
  performed by him or another would be an offense against the United
  States, is punishable as a principal.</p>
</blockquote>

<p>The premise is that there exists a federal statute criminalizing interstate trafficking of widgets, written more narrowly than the usual "affecting interstate commerce" statute. </p>
