"Actual power" really doesn't matter. Either he was interfering with the pilots or he wasn't. The criteria isn't "will it permanently blind them or not", it's whether or not he put them in danger via distraction or even temporary flash blindness. (And as I've said in other thread, possible interference with navaids.)
The way to keep our hobby legal is not to excuse or apologize for people who shine lasers at aircraft - even if it was 6mW. Or 3mW. If we want to keep what we do legal, it's best that we voice clearly and loudly that we don't condone that sort of action. Not, "aw man but it was a weak laser".
That's not the point, and it's not going to win any sympathy. When it comes down to it, the helicopter didn't "get in the way of the guy's laser" -- he pointed it at the helicopter. He was the one screwing around, he was the one doing wrong, and the power equation is irrelevant.
What's the end game in even arguing about power ratings? "Well, under 5mW, shine it at aircraft all you want" -- great, next step, thanks to a bunch of assnuts, <5mW gets outlawed.
As I've said before: I'm both a laser enthusiast and a pilot -- and I don't want either of those things taken away from me. I've heard all of the "armchair pilotage" from "cant we put special film on airplane windows" (no, we can't) to "well the windows on the plane are on top, how can a laser interfere with a pilot from the ground" (FoV doesn't work that way) to "Well it was just 5mW, it can't blind them" (but it can be mistaken for a light gun, or a navaid, or simply be distracting during say, critical glide slope interception)...
There was a recent story of some genius who was pointing a relatively weak laser -- at Boeing 737s -- as they were landing. I can't even begin to express how bad of an idea that is. Landing is THE most critical phase of flight. And you have to take things into account like decreased depth perception at night, and the runway appearing further away than that is. One distraction or a bit of temporary flash blindness can force a goaround -- which is a really risky maneuver. (Especially in congested airspaces.)
I mean - seriously - what do you do on a dark road when you have your high beams on and another car is approaching? Unless you're an asshole, you switch to low. The best policy is -- don't allow anyone to point anything at an aircraft. Not even, say, from the threshold of the airport -- Cree MC-E flashlights.
And honestly, I'd extend this to ANY vehicle. Soon as the arrests and punishments become significant enough for these aircraft related incidents, these winners are going to start pointing them at cars and trucks. (And I've said before I really am dreading the day when some idiot with a 2.5W portable IR starts pointing it at passing cars to 'see what the reaction is'.) -- And they'll keep doing it until they cause an accident. So if strong deterrents like jail time can keep that from happening, even once, then I say it's worth it.
And everyone else can avoid the punishment by simply not pointing lasers at vehicles.