The meaning of "law school sober" depends on the speaker. It can mean, alternatively:
1) having had only 1 drink
2) having had only ~1 drink/hour
or 3) not drunk enough to have done anything you'd regret
-Are you sure you're good to drive?
-Well, I'm *law school* sober...
-You were drinking for 8 hours yesterday?! It's Tuesday!
-It's cool, bro, I was law school sober.
-You went drinking with that Alaskan boy *again*?
-We were law school sober!