Two words, exigent circumstances.
Which are soon to be abused in ways “no one ever heard before”.
What I would do (or like to think I’d do) is tell them to come back with a warrant and shut the door in their face. That might play out badly for me, but I am at the stage of my career where I don’t really care a whole lot. But until anyone is in that situation themselves you don’t actually know how you’d react.
Ever notice how much grace the people who ostensibly do not trust the government give when it comes to crime and punishment?
See also: those people
This is assuming they don’t use violence to break down your door and push past.
The reality is that Trump and his minions have strongly empowered authority figures, particularly ICE and CPB. During the first Trump administration, CPB agents felt empowered to deny entry for no reason to anyone they didn’t like, which were typically brown people who looked like they might be Muslim, even if they were Canadian citizens with valid passports. In the current term, the rule of law has completely fallen by the wayside, and Canadian citizens are not only arbitrarily being denied entry, but being arrested and detained. Travel to the US is way down now that it’s perceived as a hostile country.
I think this should be the default response. Don’t let them in, but don’t actively resist them either. Just refuse to open the door, go sit on your couch, and let them break down the down.
And then raise hell about it everywhere you can.
How many broken doors, resulting in zero hidden immigrants, will it take before a backlash large enough to affect them happens?
Trump: “Here, hold my beer, and watch me!”
Before Trump, when governmental actors wished to do something it was nearly universal for them to ask:
-what law allows me to do this?
-what law limits my ability to do this?
Trump makes no such analysis. He simply announces whatever he want to do, even if it seems directly contrary to established law, and forces those who are adversely impacted to challenge it in the courts. Even if they eventually prevail, they will have suffered harm for however long the legal challenge and appeals take, and will have incurred the costs of challenging the illegal actions.
A real quality guy our Donnie is. 
There’s an excellent interview with Isabel Allende in the NYTimes today. (Not a gift link, as I’m blowing through my gift link allotment of 10 pretty fast this month.) Allende is a novelist who fled her home country of Chile in 1975 after the military coup that deposed her father’s cousin, democratically-elected Salvador Allende. In the interview she talks about her life and writing, but here she describes her experience of the coup and knowing it was time to go. I found it chilling, moving, and (sadly) timely:
I have inserted paragraph breaks that were not in the original layout for easier reading.
Interviewer: You had to go to Venezuela, because there was a military coup [in Chile]. What was the moment you knew, “It’s time for me to go”?
Allende: It took months and months. The brutality started in 24 hours — the Congress was dismissed indefinitely, there was censorship for everything, all civil rights were suspended, there was no habeas corpus, which means that a person can be arrested and they don’t have to give you any explanation and there is no hearing, there is no court, there’s no accusation of any kind, you just go to jail or disappear.
Although things happened very quickly in Chile, we got to know the consequences slowly, because they don’t affect you personally immediately. Of course, there were people who were persecuted and affected immediately, but most of the population wasn’t. So you think: Well, I can live with this. Well, it can’t be that bad. So you are in denial for a long time, because you don’t want things to change so much. And then one day it hits you personally.
For me, it was several things. At the beginning, I was hiding people in my house, because we didn’t know the consequences. We had no idea that if that person was arrested and forced to say where they had been, I would be arrested. Maybe my children would be tortured in front of me. But you learn that later.
By the time I was directly threatened, I said, OK, I’m leaving. And my idea was that I was going to leave for a couple of months and then come back. So I went alone to Venezuela. And then a month later, my husband realized that I shouldn’t go back. And so he left. He just closed the door, locked the entrance door of the house with everything it contained and left to reunite with me in Venezuela. We never saw that house again, and everything it contained was lost, which doesn’t matter at all, because I don’t remember what was in there.
But I do remember the moment when I crossed the Andes in the plane. I cried in the plane, because I knew somehow instinctively that this was a threshold, that everything had changed.
A bit close to home? Did that make you shudder? It did me.
I’m blackly amused by how much help Trump is giving China In dominating the world, economically, when they’re the big boogeyman Trump and MAGA hate.
Trump Directs Justice Dept. to Investigate ActBlue, Democrats’ Cash Engine
This received far less attention than an order to go after Hillary Clinton, or Biden family members, would have, but is much more damaging to democracy.
The current issue is that not all warrants are created equal.
There are two types of warrants, judicial warrants and administrative warrants.
In short, judicial warrants have more force that administrative warrants. Administrative warrants can be used to effect a civil immigration arrest in public, but they don’t allow the holder to enter or search private property.
This is the underlying issue behind the arrest of Judge Hannah Dugan, the authorities did not have a judicial warrant for her client, only an administrative warrant.
Trump Directs Justice Dept. to Investigate ActBlue, Democrats’ Cash Engine
The president ordered an inquiry into ActBlue, the main Democratic fund-raising platform, in his latest move using the government to target political opponents.
This latest atrocity definitely needs a lot more attention.
This from a guy who sells dinner with himself and keeps the money with no pretense that it goes for anything except to line his own pockets.
Technically, South Africa does not allow dual citizenship, although there are ways around it. Basically, “don’t ask, don’t tell”
I’m willing to bet he no longer has a valid RSA passport, so when he eventually gets deported, he’s going to meet some border officials that have no love for him. And… we in South Africa do 3rd world prisons just a shade above Equatorial Guinea.
(Completely unrelated, but fun fact - our max security prison Pollsmor here in Cape Town has a restaurant. Been a couple of times, it is part of the rehabilitation program. Us third world shitholes seem to be doing OK, Mr. Trump. And Elon se poes.)
And they literally don’t have to do anything to advance their power in the world. Just sit back, watch Trump flounder, and wait for everyone else to come to China seeking new trade deals and alliances. They know this is a huge gift for them, and they’re going to make maximum use of it.
I think the better question is “how long before a citizen is executed for using lethal force on an agent because the citizen thought his house was being robbed?”
I’d assume that the person would likely just get shot on the scene. The ICE guys will almost certainly outnumber the homeowners, and probably out-gun them as well.
So are we finally going to get the answer to whether the Second Amendment really will protect us from a tyrannical government and protects our freedom?
I’ve been wondering this myself. More disturbingly, I’ve been wondering if some in the administration are actively trying to get this to happen so they can have their Reichstag Fire moment to invoke the Insurrection Act. I’d like to be wrong about this, but I don’t think I am.
There certainly have been cases of homeowners defending themselves from mistaken no-knock raids and being killed for their efforts.
What would be new here is the raiders being ICE, not DEA or local SWAT. And maybe the raids not being on mistaken innocent targets but rather on their intended who-cares-if-they’re-innocent targets.