Interesting question, and actually the answer could be no (surprisingly). Some US nukes use varying compositions of high explosives in the primary stage. You

Interesting question, and actually the answer could be no (surprisingly). Some US nukes use varying compositions of high explosives in the primary stage. You have to set them off in a particular order, and that's the launch code (or part of it presumably). Even possessing the nukes, it would be hard to work out that sequence, since testing the explosives is destructive. And if you fire them in the wrong order, the primary fizzles and the bomb doesn't work. (I've no idea if the Russian weapons used such a system)