Unlike InDesign, in Illustrator, all Guides are locked. What if I have to select and move a Guide? How can I Unlock it?
The key to unlocking Guides is hidden under the View menu > Guides > Unlock Guides. After the Guide is Unlocked, it can be selected and moved like any other Illustrator object. After moving the Guide, it can be Locked again by going to View > Guides > Lock Guides.
Tip provided by Jeff Witchel, Certified Adobe® Training Provider.