Soak Saltwater Live Rock in Freshwater?

I live in Hawaii and picked live rock from the ocean. Friend said to soak it in freshwater for 1 hour to kill crabs and stuff before putting in tank.
My question is will the freshwater kill the bacteria also?

 

yes.

 

So eventually the bacteria will grow back though right? Like several months?

 

A freshwater dip will make it basically dead rock. But yes, it will grow back in a few weeks to months. Be careful adding this to an established tank as that now dead stuff on the rocks could cause a ammonia/nitrogen spike. If doing this then cycle it seperately.

 

Preface: I have a friend in HI. I asked him if he would get me some rock and dip it, lay it out to die, then send it to me in TN. He said that he's pretty sure that's illegal.

Question: Is that, in fact, illegal for him to get that rock for me?

Edit: It is illegal. Look Here.