Who can and can’t salute the flag during the National Anthem?

I know that prior to 2009, people in civilian dress were not allowed to salute the flag or members of the military. The new code allows for veterans in civilian dress to salute. Prior to Ronald Reagan’s Presidency, Presidents did not salute, due to the pre-2009 rule. Reagan’s gesture was continued by each President thereafter.

What I can’t find written anywhere, is whether or not a former President, who is not a military veteran, may render a salute in such situations as former President Trump was in yesterday.

On one hand, maybe former Presidents are treated as de-facto military vets. On the other hand, former Presidents, while revered and treasured, had served the country as civilian statesmen.

Does anyone have any definitive information on this?