Claine is right on...
If Antifa wants to descrate hallowed ground, it will be to their detriment in the court of public opinion. We shouldn't even be contemplating anything but letting the Park Service handle this with the L.E. powers they have.
BTW, Gettysburg is under extraordinary levels of surveillance. Not because of Antifa, but because there are millions of dollars worth of cannon barrels sitting around... and because metal detectors have caused huge damage to the grounds and to the historical record. Take a leak against a tree and they can tell your rubber size!
But we don't need to sink to the levels of those scum. If they have to sink to the level of attacking one of the most revered pieces of American history, it's because they know they are losing their argument and need to do something shocking to be relevant. They would like nothing better than to provoke violence against them... it's what they're all about.
Cheers,
Sirhr