So the question of effectiveness depends on how easy it is to pump kilowatts of laser energy at a satellite, and how much of that energy reaches the satellite based on dispersion from distance and atmosphere. Needs to be calculated. My guess is that since countries have tried creating laser defenses, someone knows.
Also bear in mind that satellites must be radiation hardened to function at all, because they're already in a high-radiation environment.
I have no doubt a military could build a weapon that could use some form of EMP pulse to completely destroy my cell phone if it were an equivalent distance from a ground-based attack site, in an environment where it wouldn't be simply destroyed. Heck, I wouldn't be surprised there's some researchers who could put something together from their test bench and bits lying around in the lab in a day or two. Doing it to a hardened target is going to be much harder.
It seems not totally out of the question. My calculation yielded an aperture requirement of 1cm for a blue-ish laser. Which yields a 50m beam at the height of a starlink satelite
