It shouldn't be activated until Walz or Frey make an outright, official declaration that they are going to fight or impede ICE. So far they've just been talking tough and playing to the crowd. Unless I missed something, there is no executive order or legislative action to get agents of the state involved in the obstruction. The best Trump can show is offering sympathy or support to "protesters", I don't think they are even supporting for the illegals themselves at this point.
I'm all for full-steam Trump 2: The Revengeance mode. But invoking the Insurrection Act is extremely serious business, and he needs to have his ducks in a row. Rushing in and pretending he can do it just because he's President is not good enough. That's the kind of overreach that could get enough GOP scared to support an impeachment.
What should happen right now is immediate investigations and arrests for the fraud in MN. Given how widespread it is, you could probably dismantle the Walz and Frey administrations out from under them, get someone to flip on their bosses, and so some very public perp walks. Nobody in the nation would have anything to defend these guys on that front.
Learn the Al Capone lesson. It doesn't matter how you take down a crime boss, it matters that you make it stick.