Yes, you can restrict users by using the Enforce Manual Typing (Avoid Copy Paste) attribute of the Lex Lookup component. Follow the steps below:

  1. Go to the records page where you have added the Lex Lookup component.
  2. Click on the Setup icon and select Edit Page.
  3. On the edit page, locate the Lex Lookup component.
  4. On the right-hand side, look for the Enforce Manual Typing (Avoid Copy Paste) attribute.
  5. Enable it and click on Save.

With this setting enabled, users will not be able to copy and paste text in the Lex Lookup component.