During WWII it was assumed that POW’s were going to try to escape. THe camp Komandant didn’t come out tell the POW’s you can try to escape if you want. The POW escape “clause” is implied. In like vein a state can “escape” the USA. It may start a war (because Yankees are warlike) but the “right” to escape is implied.
(*sigh*) I suppose it would be useless to point out that the German POWs were not governed by the Constitution?