The FDA issued a safety notice in December 2010 stating that "lasers with output power exceeding 5mW can cause irreversible eye damage, and its severity increases as the output power increases." "Although they are illegal and potentially dangerous, they are increasingly available on the Internet and in stores," the FDA noted. In normal use, the laser is probably not dangerous at all, as it is very low power and in the visible part of the spectrum. The idea is that its power is low enough that your blink reflex will protect your eyes before any damage occurs. For outdoor work, or for longer distances (up to 98 feet), green laser pointer are the best choice. Strong sunlight can wash out the red laser, so keep this in mind if you plan to work outdoors with a laser level. Another point to consider is that accuracy decreases as distance increases. Actually, yes! Laser irradiance (power per unit area, sometimes called intensity) is proportional to the inverse of the square of the distance. The idea that the inverse square law does not apply to lasers is a common misconception. However, the intensity is still inversely proportional to the square of the distance.
Generalizations about imaginary things make no sense. 500mW is enough to cause severe irreversible eye damage. 5mW is the maximum legal import limit for so-called eye-safe lasers. Even these can cause eye damage if not used properly. 10mW is the threshold for eye damage before the blink reflex closes the eye. If you take a look, 200mW is very dangerous. Laser shows are usually coordinated with air traffic control and the military to ensure controlled airspace. The answer is, no, it is not legal to point lasers indiscriminately at the sky. As long as you don't hit the cockpit, you can probably use a 5 milliwatt laser.