It won’t come down to that, and it shouldn’t. Handshake deals are illegal in the NHL and if Landy makes it to UFA there will be quite a few suitors.
How does the NHL enforce handshake deals being illegal, practically speaking?
Let's say that Sakic and Landeskog's camp make all the right noises throughout the season about wanting him to resign, but that they want to do it after the season so that there's no distractions. That's pretty common approach in the NHL, and one which Sakic and Landeskog have already been taking.
Fast forward to the end of the playoffs. There's talk about whether or not Landeskog will sign, and Sakic says that they will sit down once things have cooled down from the playoffs. No agreement is reached before the expansion draft, so Landeskog is left unprotected. Landeskog makes a mention about wanting to see what the market is like for him.
Seattle consider selecting Landeskog but get no sign of interest from Landeskog's agent, so they settle for the safe selection in Graves.
Fast forward another week or so and we have UFA day /July 1st, and Landeskog resigns with Colorado, saying that they both wanted to get it done, but with a flat cap they wanted to wait and see what the market was like before putting pen to paper. They get a solid long-term deal done without much fuss.
Now, after seeing how that narrative played out, does the NHL really have anything to point at to say that it was handled illegally? They can investigate all they like, but there's pretty much nothing to uncover, unless of course Sakic or Landeskog themselves say something incriminating (why would they?), so there's nothing the league could do.