For defense. Yeah, sure.
Defense against what, a collision ? No laser can help with that, you'd have to blow the incoming satellite apart. I don't think they're planning on adding gigawatt lasers to already hefty spy sats - Ariane would need a new class of boosters to lift all that mass. Machine guns are likely not enough either, and the recoil will really mess with the orbit and cost fuel to get back to where it's supposed to be.
So this looks more like seeing another spy sat getting into position to shoot yours, and you preempt the attack by retaliating first. That puts you in shoes of the attacker, especially if you misinterpret the maneuvering.
The whole idea is ridiculous. Much better to lose a satellite, blame it on whoever is responsible and not get blamed for the cloud of debris that will take them all out.
On the other hand, it's my government we're talking about. They couldn't get troops to Afghanistan with the proper equipment, so I don't worry much about them getting a laser-equipped satellite into space. This is just political posturing.