Lasers are rated
The least powerful ones are IIIA and IIIR
Next up is IIIB and beyond. All of these need a license. Any rating that is not IIIA or IIIR will need a variance (license)
If yo see a laser that does not have this classification, don't buy it
Chauvet and American DJ make lasers that do not need a license to operate, ergothose are the least harmful
The lasers sold at your local DJ store, are o.k. to point at the dance floor, they are supposed to be 5mW max output, some do have a slightly bit higher power laser inside, but the beam will then be split up via diffraction grating , so that any single beam exiting the aperture, will still be 5mW or below.
It is legal to point those things anywhere, allthough, it may cause some people to panic.
This is the reason you are allowed to purchase it without a variance/ permit.
The lasers you can purchase illegally , through ebay, or out of country, are typicall higher power, and require a variance, those you CANNOT operate unless it is certified by the CDRH, and you better have your variance in order, otherwise, the fine is Up to 300,000 USD, plus your opening yourself up to injury / liabilty !
Lasers are extremely hazardous in the wrong hands PERIOD!