authorized user & credit reduction

What is the name of your state? CA
I was issued a credit card from Bank One 2 months ago and they assigned me a credit line of $11,000.00 Today while making a payment online I noticed that my credit line had been reduced to $2,000 without any notification from them. I called to inquire why and was told that because I am an authorized user on 2 of my wife's credit cards that they are using that debt to reduce my line of credit(she has 2 cards with $10,000 line on each). Both accounts are in her name only, and she has excellent credit as do I. I ordered reports from Myfico.com and saw that all 3 reporting agencies have her accounts listed as joint with me. I can't call either of her credit card companies and discuss her accounts as I am not "on the account". This doesn't make sense to me. Why wouldn't this have come up when I initially accepted their credit card offer? Bank one told me that if I can get the "joint" credit off my credit report they will reinstate my credit line back to the original amount. Can anyone advise me if what they are doing is legal? I plan on calling all 3 reporting agencies in the morning to go about getting this resolved.
Thanks for any assistance or advice you may offer.
Jim

[bigun]

Yep, it's legal. Watch out-they may raise your interest rates.
Bankone has been hit hard by defaults the past year. They're also involved in a merger. They're trying to reduce their exposure. Bankone's antics are a hot topic on several credit repair sites.