I think this has zero chance of ever happening to Bitcoin, but if a country declares something to be its official currency,[...]
Think for a second. Who cares if bitcoin is a country's
official currency? Bitcoin use need only be
protected by law in a certain country to gain added legitimacy...
An affirmative law saying "yes, bitcoin is legal" would be wonderful, would it not?
I understand what you are saying, but generally, laws/statutes outlaw things rather than say what is acceptable.
For example, there is no law that says "yes, hamburgers are legal".
Attorneys may quibble and argue somehow that bitcoins are "illegal", but they are certainly not inherently unlawful, and they will not become unlawful regardless of what the ones in black robes say.