Wow. If he wrote that on the shells in the context that he was going to shoot the police with them - He is a moron. However, I think his lawyer will actually use the "He meant they are for 'Law Enforcement Use Only,' I would bet a lot of money on it.
It is legally significant in the way that it show pre-meditation. More importantly, if he reloads, the prosecution will use that as evidence of pre-meditation.
How do I know this? My uncle was shot in the stomach by a deranged eye surgeon. The prosecution used the fact that the perp (eye surgeon) reloaded his own shells as evidence of pre-meditation. It stuck too.
However, the punk is out of jail now and lives in Missouri. From what I've heard he is trying to get another practice started and his license back. I'm all about people serving their time and getting on with their lives once they have paid their debt to society. In his case, it hasn't been done though.
His botched surgeries (it was gross negligence) left several people blind and others with severely impaired vision. My uncle, as well as several others, sued him and won. He claimed bankruptcy of course and never paid a dime to anyone. From what I understand, even though he has an income now, his future earnings can't be garnished. I don't know that for sure though.