Don't do that
If you tell someone to be at work at 6:30, you're gonna have to pay them, if they show up at that time, for being there and being ready to work at 6:30. That's both state and federal law.
I have both seen and heard about disgruntled employees who turned in their employers to the feds and it ended up costing one company about a quarter of a million dollars the first time and a whole lot more the second time.
Bottom line is, if they can't get to work on time, let them go. Of course, the old phrase was (when I started), "A quarter saves your job."
Jack
Second thought
I had a couple of employees who had the bad habit of showing up 5-10 minutes late about twice a week.
They were fairly young and we got into a conversation about sports and so on and we ended up making a bet to the tune of lunch to be bought by the guy who showed up 1 second late according to the atomic clock on the wall.
I can't tell you how funny it was to see those guys running from their cars to the back door and then up 3 flights of stairs so they don't have to buy lunch.
Another line of conversation I had was with a young man who had played 3 sports in high school. I asked him what would happen if he was late to practice. He just looked at me and said, "Yes sir." He was never late again after that.
I would give him a second chance with a clear understanding there will not be a third chance. In all honesty since he is new to the job he is not familiar with the drive and giving yourself 40 minutes to drive 20 miles is reasonable especially not being familiar with the traffic, etc. I would tell him in no uncertain terms you considered not having him back and if he he is one minute late in the future he is gone.