How would a wiretap work if you sent the person notice you're listening to their phone?

Clearly some criminal investigations require not notifying the suspect.

Even so, the exceptions don't nullify the rule: find a better way to investigate, citizen rights > all else.

Countries AND the government exist for and at the pleasure of their respective citizens.

Clearly, list the specific cases instead of letting the judge feel what is appropriate is the way to go. Also helps the judge doing the right thing.