Can a lender lock in a rate without my authority?
Locking a loan does NOT require the borrowers authority.
With that said, the lender does risk locking at a rate unacceptable to you and losing your loan to another lender. It's unclear in your question that the lock was at a higher rate then you expected or that rates came down later from the original quote or locked rate and now you want a lower rate. In either case if your lender can't honor your expectations then just look elsewhere for your loan.
Your state may have legislation requiring consumers be informed during the lock process and you may want to check your state laws to determine if a violation was committed.
A good lender would not risk locking a rate without your knowledge. This might be a sign about the professionalism of the lender your trusting with a significant financial transaction.