Can soldiers in civilian clothes salute a fallen comrade memorial?

Last year the Father of lifelong family friends(their whole family are friends) passed away at the ripe old age of 91. He was a WW2 veteran and took part in the liberation of the Philippines as a machine gunner. I shined my combat boots nicely. My uniform does not fit properly anymore. But I wore my shined boots to represent his boots on the ground service during WW2. I wore my best veterans hat with a couple pins on it. I saluted the flag, the playing of Taps, and when they were finished presenting the flag to the family and just before everyone was about to leave. I moved forward with assertion so that people would take notice, which they did. Then I did a right face and stepped to the foot of his casket as to be looking at him face to face if he were standing upright, stood at attention and saluted. I then left the area with a swiftness as I was about to lose it. R.I.P. John
Posted in the wrong box a second ago. It is as it should be, now.
It is expected in this part of the country, and let them try and stop us.

What law would you be breaking and who would dare try to enforce it?

One theory is that a hand salute comes from the raising of a knight's visor plate on his helmet. (Don't know if it is true or not, but it sounds cool). As such, it showed that, the knight was making his eyes vulnerable, and thus meant no harm. A crisp, smartly rendered hand salute offered in a spirit of mutual respect and recognition of military service and sacrifice can never be wrong, can it?

From the Feb 2016 Army Echoes: Congress has expanded veterans’ rights in federal law in recent years; the most recent was the 2013 change which
affected the Pledge of Allegiance.
Respect for the Flag
During the raising or lowering of the flag, when the flag is passing in a parade or in review, and also during the Pledge of
Allegiance, there are different courses of action depending on your current status. In the instances mentioned above, all
uniformed personnel should render the military salute, and members of the Armed Forces and veterans who are present,
but not in uniform, may also salute. All other persons present should face the flag and stand at attention with their right
hand over their heart, or if applicable, remove their headgear with their right hand and hold it at the left shoulder, the
hand being over their heart. Citizens of other countries present should stand at attention.
During the National Anthem
During the playing or singing of the National Anthem, individuals in uniform should give the military salute at the first
note of the anthem and maintain that position until the last note. Members of the Armed Forces and veterans who are
present, but not in uniform, may also render the military salute. When the flag is not displayed, all present should face
toward the music and act in the same manner they would if the flag were displayed.
For additional information, you may refer to the following sections of United States Code (USC): Title 4 USC Section 4 “Pledge of Allegiance to the
Flag”, Title 4 USC Section 9 “Conduct During Hoisting, Lowering or Passing of the Flag”, and Title 36 USC Section 301 “National Anthem”

One of the first things your drill sargent says is "once a soldier always a soldier". So to answer your question, yes if a vet wants to salute he should. It's a sign of respect. I was at a dedication last month for the Gulf War memorial, All of us vets saluted. It's what we do. We give respect. We should not need a bill to pass allowing us that right. Another saying drill sargents will say "you can leave the Army/military, but the Army/military will never leave you."

A soldier that I knew personally was laid to rest. Both enlisted and I saluted him as a final gesture. There were guys that were still in outside as we were at the burial. They may have snickered because of what the rules are. I was nervous I planned on saluting too and when I got close and his mother offered a rose to place. I have no regret for that

Brothers and sisters in arms, who is going to say something? There are some places that it is the only thing to do. Think about USS Arizona memorial, when Navy ships pass, they render honors. They honor the fallen. If we chastise those who would honor the dead with a salute, we dihonor the sacrifice they have made. If we dishonor the sacrifice, we strip the meaning from the memorial. If we strip the meaning from the memorial, it becomes nothing but stone and pavement. If it is just stone and pavement, it is a waste of real estate. If it is a waste of real estate, it should be torn down and re-purposed. So imagine someone saying they want to build a mall over Arlington. That person might just be beaten to death with the blueprints. Point is it is respect for those who sacrificed all by one who fortunately came home. It is a beautiful thing.

If you're retired it's not illegal to salute in civies, in fact I wish more people knew Congress passed a bill over a decade back in which we were given the right to continue saluting as if we were still wearing the uniform. You can spot in a crowd how many retired service members know this in their saluting the colors, and when Taps is played at funerals and ceremonial memorials. I wish the services would include such information in their mandatory retirement briefings we used to get within six months of us ending our uniform service. These sayings, "Once a Marine always a Marine," and "Forever a Soldier," mean more when we all show continued military customs and courtesies in public.

I left the Army in 1988, I had spent 6 1/2 years on active duty, four of those years in West Germany ( now just Germany) I was also recalled for a month during the first Gulf War. Now flash forward to 2009, a family friend, and Korean War Veteran had passed away and I took my mother to the Funeral. That funeral was the first time I had ever attended a full military funeral, the whole nine yards the flag draped coffin, Honor Guard, well you get the idea.
When the commander of the detail advised us that any Veterans present are authorized and encouraged to render a salute to Honor the deceased. It was THAT moment right there, that it hit home what it means to be a veteran. That it up to us to stand for the fallen, to honor the fallen, and most of all remember the fallen.
Before this I didn't really think all that much about saluting the flag and what not. I would remove my hat and place my hand on my heart just like everyone else of course, but I am NOT like everyone else am I? I'm VETERAN. So after that day I will ALWAYS render a salute during the National Anthem, funerals, memorials. Not only have I earned the right to do so, I OWE it to those that can no longer do so.

If I as a civilian and veteran want to salute to show my utmost respect, I am going to do that. To hell with others. Do it.