Technically almost every white collar business traveler is working in the US illegally if you strictly apply the letter of the law. Let’s say you come here for two days of meetings and you are coding or doing some analysis on the third day before you fly home. You’ve now violated your business visa. The Trump administration can start enforcing the law like that and we’ll be even more screwed, because absolutely no non-US company will build anything if business travel to help spin up the office or plant is practically impossible.

And the same in other places. I’ve traveled to Europe many times without a work visa. I go to meetings, talk yo people and yes, write a bit of code. It’s what everyone does.

Unless you're being paid a US wage by a US company this is practically impossible to discover, other than by raiding the office/factory like they did at Hyundai.