Yes, most of us here build our own. In my state you can own lab type lasers, just handhelds are illegal.
Customs wouldn't have a laser LPM, likely if they suspected it was illegal they would hand it over to the federal police to check. Most likely you would have to have a switched on customs inspector to spot it, they would just inspect anything that looks like a laser 'pointer' or had a laser warning label on it. If it took off the shelf batteries they may fire it up, but I doubt it.
I've seen border patrol on TV, they are busy enough with people importing fireworks, efedredne disguised as baby powder, elephants feet and live animals
It's unlikely they would charge you, probably just confiscate the item. Several members here have had lasers confiscated by customs, one was asked for proof of 'legitimate use' or the item would be destroyed. In the eyes of the law you basically need to be in an astronomy club, be a physicist, science teacher or such to have a handheld laser.
Being caught with a handheld laser in public would be another story - you are basically branded a terrorist who is trying to bring down aircraft, and you probably would be charged in that case.
There was a case in the news recently where the Victrorian police helicopter (i think they only have one down there i could be wrong) got hit with a laser pointer. The pilot calmly put the aircraft on Auto pilot, spotted him with the FLIR, noted which house he went into then had a patrol car pick him up!
