Originally Posted by andrewp
On recent UA transcon flights this rule (only use the lavs in your ticketed cabin) has been part of the announcement/safety demo and is quoted as part of United's security policy. In one case I got up to walk around a little and was confronted by an FA who explained that I was welcome to walk around, but that I couldn't leave the C cabin.
If you were on an upgrade and they said "ticketed" cabin, then you were under their orders to use the lav in the economy cabin.