Nobody knows what is legal and what is illegal anymore. Having played the game and watched it very closely for 40-50 years, I can honestly say I don't have a clue what is a penalty and what isn't. Officiating in the NHL is a complete and total joke. My worst fear is sitting with someone that doesn't understand the game and having to explain the rules and how the game is officiated... Even the players and coaches don't know what is legal and illegal. Technically, I think the hip check is still legal. But if you don't execute it perfectly (and even sometimes if you do), it will be called an interference penalty or something else...

However, the main reason you don't see the Barclay Plager type hip checks is because the game has become so fast and the players are so good, it is just harder to catch someone with a hip check. And if you miss, it will almost certainly end with an odd-man rush or breakaway against your team. In short, it just isn't a good defensive weapon like it used to be. The game has evolved past the hip check, for the most part.

Youtube "Hip checks" if you really want to see some dandy's...