I agree with cbg, this would be a long drawn out process, and how much of his final time here does he want to spend in litigation over something that might or might not be a big deal?
If he was there working in a temporary capacity, (since, as you said, he had returned to work part time after a formal retirement) and they told him they do not need him any more, that was probably legal. When we say he was "terminated" I suspect this was a "we no longer need you" or "we don't want you to work any more, we're laying you off." Is that what happened? It wasn't a "you're fired!" was it?
Given that it sounds like he is on a work floor around mills and lathes and other heavy duty machine shop equipment, they could legitimately say that a person who had difficulty standing and walking around due to his weakness might present a safety hazard to the company that would justify their actions. They might be concerned about a lawsuit if he fell over dead or did something at work which he could (or his heirs could) claim had hastened his demise or worsened his condition.
But if they are by any means a large company, you can sort of bet they have thought about it before they have taken this step. Most companies are absurdly worried about discrimination/violation issues when they get an employee of this age still working. They will have had a safety consult about it, and probably HR has thought their action through before taking it.
In this situation, unemployment insurance isn't even going to be much of an easy thing, either. Because he was able and available for work until his termination, and working part time, he may set up a claim monetarily and may be able to get a doctor to state that he is able and available for equivalent work.
However, in the last few years they have made it much more stringent to continue to be able and available. There is now, in every state, a "profiling" program which picks out the claimants who are least likely to be re-employed based on their categories such as age, educational level, etc., (how's that for legal discrimination?) and causes them to be called in repeatedly for organized and monitored job search activities. He would pretty much have to swear to a lie every week, and make repeated trips in to the job search office where he would have to testify again and again that he was looking for jobs and would have to show where he had made contacts with employers for job seeking purposes.
I just do not see somebody who has been able to continue to work part time as a happy life enrichment program in retirement only because they made very special allowances for a beloved former full time employee being willing to engage in a long and contentious lawsuit against the company that allowed him to do this.
And I don't see him getting out of his sick bed and dragging into the job search office to lie his head off just to draw maybe a few more dollars for a few more weeks based on this complete lie that he's able, available and actively seeking other work, either. I'm perfectly in favor of a person being able to draw at any age if they really do meet the criteria, but we gather from the sound of this that this person is close to terminal.
