Are retirees subject to UCMJ?

The answer to that question is yes. The only example I can give on this subject was that back in 2014, the ship's purser on the USNS Arctic was caught embezzling money from the ship. He was also retired military. Because of that crime, he forfeited his pay, and has been incarcerated.

I’ve always been told you are subject to ucmj when drawing pay. I do believe that to be true.

Uhh! Yeah! Unfortunately the term G.I was penned for a reason. Once enlisted, you are Government Issue and thererfore (PROPERTY!) And IF you STILL get a check every month, yup ya bests t believe yaigttlm

9 Aug 2019
Military.com | By Gina Harkins
A new legal opinion from the Navy-Marine Corps Court of Criminal Appeals says court-martialing military retirees is unconstitutional -- and the reason concerns the issue of retirement pay.

This sucks I didn’t know anything like this wow that is crazy

The following is "pretty much" *universal:
In as much as ALL Veterans (who swore in) are potentially subject to recall for duties (rare as this may be).
In so, ALL Veterans are potentially subject to UCMJ in ANY cases * "specifically" involving The Armed Forces ie / ex secrets, security, etc.
Segway / Trivia: The US is still in a state of armistice (not peace) with North Korea ie
We have mutually remained in a "cold" state of war with them since the conflict / war initiated. As such, laws & penalties for both Armed Forces & civilians for wartime Treason are still able to be enforced.

unless it's something serious, the military isn't going to pull anyone back onto duty to prosecute them. They prefer to let civilian LEO handle it.

I thought I recently read that if a retired member who has completed all of his reserve time (30 years of total service) he was not longer considered under the UCMJ. I completed 21 years and six months active service, and have been retired from the inactive reserve for 19 years.

as a matter of fact yes it has! while stationed at camp Pendleton ca while going to the 7 day store my buddy and I saw a hit and run on base! we followed him to the stop light out side the gate! I jumped out and tried to distract him while my buddy grubbed his keys funny thing I forgot my buddy had a broken foot and didn't get there in time but he did get a tag number! I ended up on the hood of the car so I got a real close look at the person driving! the person driving was a retired master sgt he was brought back on active duty to face a court martial! where it came out he had been taking advantage of a sgts wife stationed over seas, he was found guilty and sentenced to a BCD loosing all his rank! and his pension!