My guess is that it is legal. First, an organization as large as the UAW would almost certainly check with their own tax advisors before issuing a 1099-misc. Second, there are are precedents elsewhere. For example, employer--provided life insurance (for free) can be considered taxable compensation even if provided for "free" and not used.
Here in my situation, with the Big 3 Auto companies providing the money to the UAW to provide the FREE benefit to its members, it may be something the Big 3's bean-counters INTERPRETED as a income benefit. I believe they've screwed up (on PURPOSE!) and are trying to classify it as a taxable benefit in order to write some or all of their cost off in their taxes. This Free legal service used to be available until they cancelled it a few years ago and just recently reinstated it in 2017 or 2016. I had used the FREE service once, back in 2015 and did not receive a MISC for the FREE legal service provided then.