It doesn't, of course, as you already know. But many people - at least all libertarians and strict constructionists - would point out that nowhere in the constitution does it say that a state *doesn't* have the right to secede from the union.
The constitution wasn't intended to outline what the states and people can or cannot do. Its intention was to outline only what the federal government specifically can and cannot do, and states that all other matters not specifically enumerated in the document are left to the states and the people respectively.
Of course that truth was tossed in the garbage long ago, and Abraham Lincoln had a great deal to do with that. Most all people today, regardless of their political stripes, can see the truth of this is quickly and name something that they feel the federal government has no business being involved in.
BTW, there is no question at all that Texas has the right to secede from the union. It is in the Texas constitution.
But, back to trains. Just for kicks I ordered an On30 Confederate train set the other day. It looks really cool. The boxcar with the picture of Robert E. Lee appeals to my anti-federalist streak.