When to validate if the set of items selected totally valid for the operation?

Case: enterprise web-client solution for sales orders, the User needs to select lots of items to perform one operation in bulk and not all the items are applicable for this operation (due to hidden parameters, status, etc.). Please advise, which practice is better to follow: A) allow user to select anything/all and let the backend validate the selection and if any not suitable item is found - rollback the operation dropping the message listing the items caused the rollback. B) validate the selection on UI on click of the button allowing to send to backend only the 100% valid set of items, so backend will not fail.

So far we can choose only from these options because of the performance issues.