Mr. Benning wasn't very bright, was he?
He thought reposessing fugitive slaves and being allowed to take slaves into the territories would be easier across international boundaries than state lines?
LOL
It would have been easier if the Confederate States Army crossed the border first, which was exactly the intention of the more militant leadership. They were expansionists and made no secret of their desire to colonize, by force, Cuba, Mexico and even all of Central America. They first had to dispose of the 'pasty-faced mechanics' in the Union Army which proved to be far more difficult than the Fire Eaters of 1860 promised.