“None of the rules appear in Customs written requirements.”
I imagine if they just pay the $500 annual boating fee to the agent it would be a lot easier than all of those forms and permits. Oddly, the fee isn’t in the requirements either.
I had to look at the map to see the relation of Skagway and Haines. It would be like having somebody land at LAX, clear customs, and be told they have to report to Customs at Disneyland. You would have to go a ways to touch Canada again requiring a customs inspection