There is no scenario in the foreseeable future (decades) to have a laser powerful enough to kill an incoming nuclear warhead. For the simple reason that the ree

There is no scenario in the foreseeable future (decades) to have a laser powerful enough to kill an incoming nuclear warhead. For the simple reason that the reentry vehicle is designed to withstand the enormous amounts of heat released during the reentry. It is very unlikely a laser can put a comparable amount of heat on the reentry vehicle, and do that from hundreds or thousands of miles away. Given that, the only time an ICBM is vulnerable to a laser weapon is during the takeoff time. During that part of the attack, the ICBM are protected by the atmosphere itself. A laser maintains its power very well in vacuum, but not in air, especially if there are clouds. So, one needs to be close to the launch point. In other words, you need a very dense network of satellites that would carry these lasers to provide the coverage necessary. Even with such a network, it would be quite trivial to come up with inexpensive countermeasures: simply launch more missiles, some of which do not carry warheads.