Difference between establish and permit

They are related but not identical.

Establish

means

creates the legal rule itself.

Example

Parliament passes a law saying:

Citizens may vote at age 18.

The law establishes voting at eighteen.

---

Permit

means

something is legally allowed because the rule already exists.

Example

Because that law exists,

an eighteen-year-old is permitted to vote.

So

establish → creates the rule

while

permit → describes what follows from that rule.

That is why legal scholars often prefer

"The Amendment establishes an exception"

rather than

"The Amendment permits..."

because the Amendment is the source of the rule.