This is nonsense and I would be furious if it happened to me.
According to the Star Alliance website, the following is stated under the heading "Star Alliance Gold Customers Travelling in Any Class":
"Continental, United, and US Airways Star Alliance Gold customers may only access the Presidents Club, Red Carpet Club and US Airways Clubs within the U.S. when travelling in conjunction with a Star Alliance international flight."
The link is here
http://www.staralliance.com/en/benef...access-policy/
No mention of C/F being necessary.