Oh come on...
We already have to dance around wondering if simple things like port scans are legal or not and WiFi packet capture. Now we have to worry about packet analysis?
Pentesting is going to become a joke if every one of the methods used for reconnaissance becomes a grey area and requires specific permission and disclosure to execute.
Pentester: *sneaks into office building, spends a while navigating the building and observing, finally reached target PC*
Pentester: Hello Sue in accounts. I am here to perform a penetration test to gauge the level of security on your company network. Please sign this form to give me permission to attempt to access your PC. I will also be plugging in a USB keylogger and ethernet wiretap that you should find suspicious, they look like this. I will be assessing to see whether you notice them and report them in accordance with the IT security policy.
I may also send you phishing emails and attempt to social engineer you into handing over credentials without due care. The telephone number I will call from is 555-123455 the email address the phishing attack will arrive from is email@example.com.
Please sign here if you agree to be tested, and sign here to confirm that you will at least try and work normally now that you know you're under attack and specifically how I am going to attack you.
Cop: FREEZE! GET DOWN IN THE FLOOR AND PUT YOUR HANDS ON YOUR HEAD.
Pentester: Dude, I've been hired to test this company.
Cop: All your methods are illegal!!!!