Sure is. But, USERRA is only valid in the land of unicorns and rainbows. In the real world, at-will employers wipe their @ss with USERRA. You'll never prove it in court either. Ask the weather channel chick, and she was hittable and had a public podium organic to her vocation. Besides, do you really want to work at a place you had to sue in order to retain employment in the first place? USERRA is a non-issue when you're a non-rated one weekend a month, two weeks a year kind of reservist, which is about the only military participation most civilian employers tolerate. Otherwise, for the rated types, it's a catch-22.
If you're not an airline guy or a co-located civil servant, don't bother with the reserves honestly.