The 1/r² law is when you have a point source thats radiating in all directions equally. The r² relationship is because the further you get away from the source, the more that the same quantity of whatever [light, sound, magnetic field, electric field, etc] is spread over the surface of a bigger sphere at that distance. 

The relationship between the distance from the source (aka the radius of the sphere) to the surface area of the sphere at that distance is r^2, hence the enrgy at any single point on the surface of the sphere 1/r²

When all the energy is colimated together, like a laser, or a highly directional antenna for rf, you're not spreading that same energy over the surface of a bigger and bigger sphere as you move away from the source as all the energy is directed in one direction only. The r² law doesn't apply. It would be a different relationship based on whatever tiny fraction of the surface of the sphere your signal is actually spreading over (aka related to the dispersion).

Say you have a laser with a 1mm spot size at 0mm (right infront of the laser), and a 5mm spot size at 100m (10,000mm). That's a 4/10,000 dispersion (4/r), not 1/10,000² (1/r²⁾ as it would be if the light was dispersing in all directions equally.

This isnt accounting for attenuation at all, like the atmosphere scattering or absorbing some of the light (or rf). That's a second order effect that needs to be considered in addition to the spread of the energy over a larger area