In CT you can terminate someone while they are fighting a Worker's Comp claim - it happened to me. My doctor ordered me out of work - the company was fighting the claim and they terminated me because they claimed I "refused" come in to work. It was a mess! Since they were fighting the claim they also didn't have to pay me comp while the dispute was going on. The whole mess took almost a year to come to an end. They just hope that you'll run out of money and stop fighting!
The same general rule of treating everybody the same in similar situations would also apply to a reservist called to active duty. IF this reservist's job was eliminated as part of a restructuring or downsizing--meaning that other non-reservist employees were also terminated at the same time as he was, then this terminated reservist will have a hard time winning any discrimination case.