In general, the cardinal rule of operating high powered lasers is: do not to shoot lasers AT people. In the US, laserists are required to keep the lowest laser beams about 3 meters above the floor, so there is a few feet of clearance between a tall person and the bottom of the display. Laterally, a 2.5 meter clearance is observed.
If you want to “crowd scan” or intentionally shoot lasers at people, different countries have different rules. Again, in general, there is a concept called MPE which is an amount of power under special conditions that it is safe for the human eye to absorb. Most of the world observes this standard, though enforcement is spotty. In the United States, limiting audience scanning to MPE levels is the law, and is enforced.
Beyond that, US law requires, and best practices in the rest of the world dictate, that you have a reliable means of stopping the laser in case of emergency. Meaning that the laser operator has at least a base level of training to be able to run the laser safely, and that certain procedures for setup and alignment are observed. Most of this information is included with each laser system we deliver to a customer.
The vast majority of these regulations are quite simple and easy to learn; it is certainly much easier than learning to drive. Doing MPE crowd scanning is a little trickier and requires some specialized training to accomplish safely.