Ideally it would be a constitutional ammendent, stating that privacy is a right of every citizen, and a human right.
Legislation to the right to encryption would then just follow from it, but having it in the constitution would make it harder for future governments to pass certain kinds of legislation, or if they pass them, the supreme court would declare them inconstitutional.
That is a good example of a misdirection play, a polarizing discussion point that political opponents get hung up on, which you never ever intended to actually pass, and you'll happily drop it later, but it helped relieve political pressure from other potential hot topics. We see typical conservative tactics being employed against the conservative base :)
The problem is defining "privacy" though, isn't it? What, specifically, would the amendment require or prohibit under the banner of "privacy"? How could this definition, if enshrined into nearly immutable law, be modified to account for a changing technological environment? How do you prevent such an amendment from suffering from the fate of the US second amendment, which in many places is honored mostly in the breach?
This should be the goal. In the days of the internet, mass surveillance, nearly eradicated privacy we need a right to have and use strong encryption without any backdoors.
Legislation to the right to encryption would then just follow from it, but having it in the constitution would make it harder for future governments to pass certain kinds of legislation, or if they pass them, the supreme court would declare them inconstitutional.