People treat these two words as spelling preferences. They are not. They describe two different kinds of right, and the difference decides what a government is permitted to take from you.
Unalienable
A thing or right that cannot be transferred, surrendered, given, taken or sold, and crucially, not even with consent. The law dictionary definition is blunt about it: incapable of being alienated, that is, sold and transferred. Such a right is intrinsic and inherent to the individual. You cannot sign it away, because it was never a possession to begin with. Every individual has unalienable rights.
Inalienable
A thing or right that cannot be transferred, surrendered, given, taken or sold without consent. Which means it can be, with it, actually or constructively. Rights of this kind are not inherent in a person, and can be alienated by government. Persons have inalienable rights.
Which word the founding document uses
The Declaration of Independence holds it to be self-evident that all are endowed by their Creator with certain unalienable rights, among them life, liberty and the pursuit of happiness, and that governments are instituted to secure those rights, deriving their just powers from the consent of the governed.
That is the strong word. It is deliberate, and it is doing a great deal of work.
Which word your state uses
Most state constitutions recognise only inalienable rights. Read the sentence again with the definitions in front of you and the implication is uncomfortable: a right that can be alienated with consent, in a system that is extremely practised at obtaining consent.
Consent can be constructive. It can be buried in terms you did not read, in a form you had to sign, in a condition attached to something you needed. If your rights are inalienable rather than unalienable, then every one of those moments is a place where something can be taken from you lawfully.
Why this is worth your afternoon
This is not a semantic hobby. It is the difference between a right that precedes government and a right that is issued by it. The first cannot be legislated away. The second can be, and historically is, one reasonable-sounding exception at a time.
So the question to put to any government, federal, state or local, is simply which of the two it thinks it is dealing with. The answer tends to be revealing.
