Answer: INALIENABLE (or UNALIENABLE)
Notes/explanation:
The final version of the Declaration of Independence uses the spelling unalienable. That was the copy of the document as transcribed by John Adams, which was used for printed copies to be made. Thomas Jefferson's original draft used the spelling inalienable. The two variations of the word were both in use at the time in the 18th century. Either way, the word means something that cannot be made alien to you -- in other words, something that cannot be taken away from you.