[JumpCrisscross]

> the "use of it" is obvious, it's another protectionist tariff in a long, long line of protectionist tariffs

I’d be curious for contemporaneous accounts over someone a century later guessing what may or may not be obvious. Maybe a cabal of industrialists conspired. The Foreign Dredging Act does predate trustbusting. Or maybe there were military concerns. Not an issue in this particular case, but one can imagine outrage if e.g. China controlled the world’s dredging fleet and threatened to isolate America’s ports in retaliation for some Senator’s mean tweets about Xi.

[ldiracdelta]

Bingo.

From my readings, the reason certain parts of shipping are mandated to be constructed in USA is that we Americans don't want to lose the ability to construct war ships. Tariffs may not be maximally efficient from a theoretical free trade perspective, but the cost premium of a tariff forcing local production may well be worth it compared to losing your ability to protect yourself on the seas.

Now, whether you agree with that sentiment or not is orthogonal. Chesterton's Fence says that if you don't understand why this law exists, then you don't get to tear it down until you do understand why it was ever thought to be a good idea.