I realize the US Constitution only means whatever the heck the Supreme Court says it means, but Article 1 is explicit in preventing both the federal govt and the states (which is relatively rare, most of the restrictions on states are a result of the "incorporation doctrine") from passing ex post facto laws. And I think this prohibition was made specifically for purposes like this, where you shouldn't be penalized if you plan things above board according to the law at the time your decisions were made.
I sign a contract to import widgets, but they have not been delivered yet. Congress imposes a new widget tariff. Should I be able to import my widgets without paying the tariff?
The linked article states the bill (which has not been passed yet) says this (emphasis mine):
> effective for all sales taking place at or after Sept. 13, 2021.
Using your example the equivalent is imposing a widget tariff, passed at date X, for widgets that have already been delivered at some previous date X - N.
It is equivalent to announcing a planned widget tariff on date Y, for widgets delivered on date Y and later. Because if you announce it on date Y, but it doesn't go into effect until formally passed on date X, people will import a whole lot of extra widgets quickly to get around the new tax.
> Because if you announce it on date Y, but it doesn't go into effect until formally passed on date X, people will import a whole lot of extra widgets quickly to get around the new tax.
So? I mean, my answer to that is, "tough shit". Doesn't matter when it is "announced", there are a million things that are announced that never make it into actual law. And there have been many tax laws in the past that have not been ex post facto laws, and yes, people take advantage of the current situation before the law changes. That's literally exactly how a fair legal system should work.
At some point people will want new widgets again, and they will have to import them after date X, and that's when the government should fairly be able to get their extra pound of flesh.
