As I said, Law has a better fruit that gives him mobility and evasion. And law should know BB's power to some extend. So law won't just stand there and get pulled. He WILL evade using room and shambles etc... The nullification only works when he is touching them, not when pulling. And Ace was a little cocky and totally unaware of the Darkness fruit, and he was a hothead who was looking for vengeance too. That's not the case for Law at all. He is a calm analyzing fighter. He should have no trouble with evading the darkness pull.
Think about this, Blackbeard, went to Amazon lily. His first full fledged appearance in post time skip. And ge didn't get to showcase his abilities and his mastery over them at all. Here we have an opportunity to see those things. But if Law gets folded with just the same abilities it tool for teach to put down Ace, that's not gonna be interesting at all. And if this is to be Law's final showdown (I don't think it is, but if it was), then oda would sent him off with one last hurrah.
All I'm saying is BB ain't gonna low diff Law.