Lev 27:29 'No one who may have been set apart among men shall be ransomed; he shall surely be put to death. NASB
What in the world does this mean?

I have been reading commentaries, and they all seem to say that these are people who are set apart on a sort of death sentence. For say, blasphemy or something comparable. I can't put this together from the context though.
The ESV even renders it this way:
Lev 27:29 No one devoted, who is to be devoted for destruction from mankind, shall be ransomed; he shall surely be put to death.
But I must say, that's a lot of text to add.
I would appreciate any help you guys might add.
God bless,