Ah okay I can see the confusion. The line reads: "I grinned. Even if he was mature enough before, the stupid law said he needed another year. Now he had plenty." (At least in my current version. If it was re-written, my bad.) She's recalling the time he was 20. I'll fix to be more clear.
Okay, now it reads: "I grinned. The last time he was here, he still needed another year to drink legally. This would be his first \"brew.\""