Usually, you will not get completely indemnified financially. Legally, though, yes. Having a green card to do physical testing is a lot of fun. Some of the time the police do get called or whatever, I have stories. But, the short version is.... nothing happens. You have contacts high up at the company. You have a contract. It spells out you will be doing these things. You usually get paid some amount up front. It's enough to not worry about it very much and just do your job.