You highlighted the wrong part. I agree with the above statement -- an unalienable right cannot be taken away, at least, not without individual due process. The unalienable rights to life, liberty, and property are an example.
But the right to keep and bear arms is not an unalienable right -- how can we forbid all 16-year-olds from buying a gun? Can we take his life? Can we lock him up? Can we take the property he, for example, receives in a will?
The RKBA is a fundamental right, protected (or not) by the state.
The RKBA is a fundamental right, protected (or not) by the state. "
A State has the (reserved) power to decide when a person is responsible enough to have a gun, just as when he's old enough to handle other deadly weapons. Determining the age of majority, consent, responsibility etc. is one of the few remaining (unstolen or undelegated) State powers.
Generally speaking, an unalienable right is a right that it would be immoral to take away without consent.