I'm all for open borders and one day country borders should be as easy to cross as state borders but there are large costs to being the only country to not screen out ax murders, terrorists and such as you might get undesirables deliberately dumped on you.
That doesn't mean invasive checks necessarily but at least retaining the option to go kick ppl out and deny certain entries once such hijinks are discovered.
Wouldn't the same judiciary that addresses native-born axe murderers and terrorists* serve in this purpose? What's special about immigrants, exactly, that a separate apparatus is needed?
* — Naively assuming the state can distinguish, of course.