Any experience in working with aged emeritus supervisors? Recently, a graduate position, supervised by an emeritus faculty member has been offered to me. The aforementioned professor is one of the most famous contributors of his field on the planet for over 3 decades, but his age is over 75...

Some people just advise that the old faculty members would not capable of the active research and support of the graduate students and one better tries to inhibit cooperation with them.

The others asserts that the worthy and coherent experience and cumulative knowledge of such people shall be grabbed by graduate students by working with them!!!

I just struggled to contact with his current and former students to know his code of ethics, specifically, but they refrain from answering me.

Does someone have any experience to pass graduate studies under supervision of such aged emeritus faculty members?
Quick Answer: The downside might be his age, but the upside is plenty! 

It is obvious that the age might be a factor, however you are not dealing with a dance instructor or a body builder here. Look at Prof. Stephen Hawking, beside his age, there are other limitations; but everyone listens to him and want to learn from him. Put his name on a conference, and people will line up. The following points popped up in my head: 

Experience: Being dominant in a field for any amount of period, let alone 3 decades, is not easy. What you will get is a world of experience and vision (my second point here). 

Vision: It is not all about hard work to be on the top, the individual needs to have a vision of the field as well. You will have the privilege to lean how he come up and deal with research issues. Believe me, I had supervisors that did not have the 'vision' part, and working with them was not pleasant. 

Less Politics: He already 'done it all', and therefore not looking forward that much to the next promotion or something of that sort; what you get is a person that everyone knows that he is the leader in a field; so all the help you get you from him; you get it through no or much less jealousy and/or office politics. 

Decision On Your Overall Career: If you get a position to work with a young supervisor, you can't truly answer the big question: What I will do after my PhD?. However if you work with an experience academic, you can see yourself after 20/30/40 years. You can see how hard you need to work to get there and is it something you want to do or not. 

Conclusion: Take the position, there might be a little downside because of his age, but the positive points are plenty.