Ah yes this is the problem us hobbyists have to face all the time. We get new members looking for places to purchase dangerously powerful lasers. Sadly many are very young. We try our best to educate but not many care.
Difference is that there's already laws in place guns that are super strict about age. While lasers have regulatory laws on final equipment (key interlocks etc) there's basically no law that regulates the selling of laser components. Most bare laser diodes you can find on eBay advertise their components as exactly that, components. If you are going to incorporate that component into a final device, it's your legal responsibility to put the required interlocks in your device before selling the final device to someone. If someone melts their eyes out, and you didn't put in the proper safety features, you'll get sued. The person who supplied you with the component has no liability. They fulfilled their legal obligation when they included the disclaimer that what they were selling were just components, and that it was the responsibility of the person buying those components to incorporate them into a properly designed device. This is why those sellers of high power laser diodes are not breaking the law. They don't sell them as finished products (even if hobbyists buy them and use them for that very purpose). With their disclaimer posted, they've fulfilled their legal obligation, so they can't be sued out of business if you burn out your retinas.
