It would be like WWI, when they had “Slacker Raids” to try to catch the draft dodgers.
I didn’t know about those. Interesting. I wondered about it generally, because in 1917 huge swaths of the US were pretty backwards, there was a Census and births recorded, but no national database of addresses and the rest of it. A whole lot or people could fly under the radar. “Social Security” ended that, I reckon. A lot of children died, too, when SS numbers were required for federal tax returns about 1980. Weird, that.
“You can’t yell Fire in a crowded theater” was the example used by a Supreme Court justice, in response to World War I anti-draft demonstrations.