united-states
In the US, can a manufacturer enforce how their products are used?
<p>Petzl (a company manufacturing outdoors equipment) has the following <a href="https://www.petzl.com/US/en/Sport/Self-belaying-is-prohibited-" rel="nofollow noreferrer">statement on their website</a>:</p>

<blockquote>
  <p><strong>Self-belaying is prohibited!</strong></p>
  
  <p>We cannot ignore the fact that some people use the GRIGRI as a
  self-belay device. Many internet sites give tips on modifying your
  device for this use.</p>
  
  <p>Above all, this technique increases the risks to the climber. Firstly,
  the climber does not hold the brake side of the rope. </p>
  
  <p>Additionally, in case of a fall ,the GRIGRI can be blocked against the
  rock, the positioning system (positioning strap), or other, thus
  negating its braking function. The climber could fall to the ground.
  Finally, <strong>remember that any product modification outside of Petzl
  facilities is formally prohibited</strong> (see Instructions for Use). </p>
  
  <p><strong>Self-belaying with the GRIGRI is prohibited.</strong></p>
</blockquote>

<p>Are these provisions actually enforceable, in accordance to US law? If it matters, Petzl products are sold in regular stores that don't require customers to sign an explicit waiver before making a purchase.</p>

<h2>No</h2>

<p>It's your device, you can do what you like with it (subject to the law - you can't hit people with it. Unless they want to be hit: whatever turns you on, turns you on).</p>

<p>However, if you do operate it outside their instructions then they would not be legally liable if it failed and injured you or someone else or set fire to the cat or whatever. The "prohibition" would limit their legal liability.</p>

<p>This would be very unusual but if the device were rented or leased rather than sold the manufacturer could impose constraints because it remains their property.</p>
