Can a job terminate you for going to meps?

Update: his job was only upset of the short notice he gave when they kept him overnight. Thankfully, they were understanding and allowed him to take a day off next week to go back. They even gave him a make up day for his hours.

Sadly, since your husband is not in the Service, his job can do it. However, I would recommend your husband review the USERRA laws to have a better understanding.

Yes. They can fire him. The long and short of it is that he is going through the process of joining the military. Nothing in that is protected by law. Nothing. Sucks but that is simply the way of it. The letter his recruiter provided means nothing. It has and bears no legal weight. It is simply a letter stating that your husband was at location X for this day.

Here is where he has to evaluate what is important and what is not. Is he looking to go active duty or is this a reserve enlistment?

Yes, his employer can fire him but there is a process for it. Depending on the state and that states laws is going to determine what rights your husband has. I would suggest that your husband go in and talk to his HR department ASAP and work things out. If he has vacation time have him take that or some companies have sick and personal days.