As came up in one thread I have had a customer or two in Mexico. I won't get into all the technicalities of legally doing that. I'm sure it all changed anyway. It did a couple times over the course of time when I was working in Mexico.
One day working on time and materials they had me "supervising a trench that needed to be dug over to a guard shack for cameras and network cable. The site managers told me, just make sure it gets done. We do not expect you do anything but supervise. They were basically paying me by the hour to just stand there.
I told the workers the trench needed to be three feet deep. I grabbed a push pull rod out of the truck and marked it at three feet with a piece of tape. They got to around two feet and the guy with the the gage would jam it hard into the bottom of the trench and with the tape mark still above the pile of dirt next to the trench ask, "Ta bien?" After about fifteen times of this I grabbed a pick and a shovel out of my truck and jumped down in the trench.
I dug a short section down to a little over 3 feet and called out, "Esta aqui es bien. La otra es mallo." I saw a few frowns, but I ignored it. They were paying my hourly rate, and I was already in the trench so I just kept digging. As I worked I noticed the various workers were disappearing to other things. When I got about half way down the trench I met up with one older guy who was still working. I looked past him to see the rest of the trench behind him had been properly dug down to an acceptable depth. As we clear the last few shovel fulls out of the middle we looked up and he grinned at me. He didn't say a word, but to this day I believe he was thinking, "Yeah! You didn't out work me gringo!" He made me grin too.