Let me set a few things straight here.
Hundreds of captured CS flags went to the US War Department during the war. They were returned to their respective southern states in 1905 and those that could not be identified went to the antecedent organization of what is now the Museum of the Confederacy.
Hundreds more CS flags were sent to respective northern states during the war and many remain up North still. Some northern states sent flags back south in the middle to late 20th Century and some still remain, almost all of them in museums large and small.
Hundreds more CS flags are simply missing. Some from Southern families and some sent to northern families during the war.
I have been in most of the northern museums that still hold CS flags and know people in those that I have not been too. You are simply wrong when you state that these flags are not taken care of! Most of them are in just as good and proper storage facility that costs these museums thousands of dollars to put into place just so they can properly take care of these artifacts according to proper museum standards that all accredited museums adhere to.
I have worked for a state museum and have consulted for many other state museums on Confederate flags and have an extensive list of people in them that I know and deeply respect and you have insulted both them and their museums by your ignorant blather!
Some of these museums, like the New York Military Museum for example, have spent thousands of dollars properly conserving these captured flags as if they were flags for New York units. Iowa has worked hard to document their CS flags and properly care for them in climate controlled environment that also protects their cherished Iowa unit flags!
What museum has burned captured CS flags? What museum is allowing them to rot away for any other reason than proper funding to care for them? Do you have any clue how much caring for these flags costs?
There is no law that could stand on any legal footing that would force people or states to send anything they have back to any other state - nor would I ever support such a law! IF these states CHOSE to send them back then fine. Massachusetts Historical Society sent back a number of captured CS flags some years ago and I consulted with them for most of these returns. But make a law to FORCE them to do this? Puuuhhllleeeezzzeee!
Regarding private property, that is a cherished right in this nation and hopefully it always will be. If a family has a flag and they want to sell it then who are you to say they cannot? How about if I take offense at you selling your car?
Would it be wonderful if all these flags were in museums? Sure would be! But I am also a realist and that is just not going to happen. One major collector spent a few million of his own money and built a sate of the art Civil War museum in Ft. Worth, Texas to house his huge collection. This is the Texas Civil War Museum and it is excellent! Other collectors have loaned their flags to other state museums and they are happy to do so. Many museums have solid relationships with collectors and they really appreciate what these people do to document history. A lot of material would simply be lost if it wasn't for many of the better collectors out there!
A lot of captured flags rest in lots of other places as the spoils of war. This has been going on for hundreds of years. England still has captured US flags from the War of 1812. Shall we invade them to get them back? The US still has captured Mexican flags from both the Texas War of Independence and the Mexican War as well as the Texas-Mexico war of 1842 - and they still have captured flags from all three events as well. Would it be nice for a big swap of flags to take place? Sure. Will it happen? Not likely. North Korea still has a captured US Army regimental banner from the Korean War taken in the Chosin Reservoir campaign and I doubt we will be seeing that flag back in the USA any time soon.
I hope this has set the record straight somewhat.