Can children now buy M rated games?

I'm very confused about how the Supreme Court decision works. Does this mean that a child who's under 17 or 18 can just go into a store and pay for a violent game and just walk out, or does it mean that a store that is willing to sell a violent game won't be fined thousands of dollars or does that mean that essentially nothing has changed in terms of minors getting violent video games. Any clarification would help a lot.