Have you got that in writing?

For the record, you did NOT lie to immigration as you honestly believed that was what you were entering the US for.

How long are you here for? That would make a huge difference on how to react, IMO. If it's for a couple of weeks, then I would go for it and question the decision on my return. It also depends on what you're expected to do while you're on-shift. If it's more of an advisory capacity, there's probably no issue with it.

I would be keeping all my options open at this point until I had further information, but I do agree that it would be rash to hand in your resignation.

Don't resign. Let them fire you, then you can claim unfair dismissal. Otherwise, you're stuck trying to prove constructive dismissal if you resign when you return to the UK.

You can't do the work.. They need to know this!

This is an area that has confused many people including me.

When I lived in Canada and was working there on a temporary work permit, my boss sent me to the US to install our computer system at client sites and do the on-site training - teaching users to use our software. So I was most definitely doing work in the US - but on behalf of my Canadian employer who was the one paying me. That's exactly what I told the US immigration officer I would be doing and he didn't bat an eyelid.

If you were being paid directly by the US employer, then you would definitely be doing wrong. I think as long as you are NOT being paid directly by the US employer, then this starts to move into a very grey area for a lot of people. I'm not saying it's right - I'm saying that you'll find that you get different answers because of confusion.

You didn't actually lie to US immigration. You believed that you were telling the truth. A lie is deliberately saying something that you KNOW not to be true at the time you say it. However, now you actually know something different.

I honestly don't know what I would do in this situation. It is definitely worrying that, after communicating your concerns, you were immediately threatened with being fired. That is not the sign of a healthy working relationship with your employer. If what they are doing is legal, then they should have been happy to have someone (e.g. an immigration lawyer) put your concerns to bed.

If you are going to resign anyway, then I definitely would not do the work. I would let them fire me and then they deal with the consequences in the courts.

If you want to keep this job (and I'm not seeing any reason why you would considering the aggressive response you got to raising valid concerns), then only you can decide what to do.

Wow, I just read through this discussion. One thing not mentioned by the other posters is that when (not if) Immigration finds out about one of you not working according to the law (assuming that's indeed the case), they are likely to investigate, and then you'll all be in trouble. So it's more than just "should I keep my head down and not make waves". Waves might be made because of someone else's case no matter what you do in your own case.

My current and former managers are from outside the US, and they each spend about one week a month in my facility. I know that one came in and out until they were cautioned at the border that they might be required to get a visa soon, so they applied for the visa and traveled much less frequently until it was approved. I think the other has no work visa. The definition of "work" will vary by job description, but my current boss attends meetings, supervises the team, writes e-mail, and works on documentation and planning and support, that I know of for sure. I don't know whether or how much it matters that either of them also travel to other countries for business meetings and training other staff. When I traveled to the UK, there were laminated posters everywhere in the facilities I visited cautioning overseas workers that they needed to have the proper visa (which I had; come to think of it, it expires today). But I haven't seen any similar postings here in our US corporate office.

MarylandNed, it doesn't sound like you were doing anything to fall afoul of the law anyway, as installing and training users to use the newly installed computer systems is perfectly acceptable, as it happens. But if you were to stay and do some other sort of work (participating in a documentation project, for example), then questions might legitimately have been raised.