Thanks for the responses --
I have a 2017 Macbook Pro with 3 external drives hooked up -- 2 SSD thunderbolt drives; a 1 TB GB and 256 GB each connected to a USB-C port, and a regular HDD drive connected to a USB port for regular daily computer backups.
On the 500 gb drive I can move files freely to and from it and my Macbook, and same goes for my HDD computer backup drive. But when I want to make copies of files from the 1 TB GB to the 256 Gb drive connected to another USC-C port, Sierra always asks me to authenticate with fingerprint ID or password -- not only to copy files to, but to delete files (move to trash).
In disk utility on the 256 GB it says the owner is "enabled." The 1 TB says the owner is "disabled."
So I guess the question is: why does the 256 SSD drive, and only that drive, not let me freely move files without asking for authentication? Does the disabled and enabled thing have anything to do with it?
Thanks again for any ideas--