On St Patrick's Day, Lenny is seen both at Moe's bar right from when it opens at 9am and at the street parade where Bart get's drunk. Then he is immediately seen again at Moe's when Bart is shown drunk live on the news channel even though each scenes occur simultaneously.
When Bart gets drunk at the parade and Marge grabs him, the caption on the screen says "Drunken boy -- live". However, in the next shot we see the entire Simpson family, including Bart and Marge, watching this on the TV in their living room (i.e. Bart and Marge watching themselves on TV). Obviously, it's not really live.
Although the prohibition law had been repealed, Homer still produced and sold alcohol without a licence, so he shouldn't have been allowed to go completely free.