Is a license necessary to produce patented inventions?
<p>Say I am a malicious CEO of <code>Company A</code> which has patented one of our products.  At a later point in time, I then <strong>publicly give <em>verbal</em> permission</strong> to <code>Company B</code> to produce this product.  (Permission is not given over any other avenue of communication)</p>

<p>After <code>Company B</code> has made a fortune off of our product, would I be on good grounds for infringement?  Does it change if I have given them <em>written</em> permission but not filled out a licensing agreement?</p>

<p>In short, <strong>can I use anything besides a licensing agreement to give permission to produce a patented product</strong>?</p>

<p>If the answer is different from country to country, then assume we are talking about US law.</p>

<p>You say the permission was "public", therefore I am going to assume that it cannot be argued that there was no agreement.</p>

<p>There are two possibilities:</p>

<ol>
<li>If Company B has given consideration for the promise then there is a binding contract and Company A <em>may</em> be able to end it but could not seek redress for when it was in place.</li>
<li>If there is no contract then the principle of <a href="https://en.m.wikipedia.org/wiki/Estoppel#Promissory_estoppel" rel="nofollow">promissory estoppel</a> should have essentially the same effect.</li>
</ol>

<p>An agreement, including an IP licence, does not have to be in writing nor does it have to have any particular form.</p>

licensing patents