Erase USB in Disk Utility says "Permission denied"

Question

I'm trying to format my USB so I can get all the space back onto it, but every time I try to erase it in Disk Utility, this comes up:

POSIX reports: The operation couldn’t be completed. Permission denied

Answer 1

Try with diskutil:

diskutil eraseVolume HFS+ "new name" disk1

^{Replace new name with the name you wish the disk to have, and disk1 with the disk identifier (select disk → Info).}

Answer 2

Although it may seem unintuitive, try formatting the drive using a Windows computer. Then, take the now (Windows) formatted drive over to the Mac and format it there - it will work.

It's has happened to me many times too, but the speed of this method has always greatly outweighed any further research time.

I hope that helps you out, however, the question of what causes this error could be one of many... hence, if you need a formatted drive now, this will work.
But do let me know how you get on.