I've worked for an image agency where I've done retouching on several celebrities. I did not have a portfolio prior to said job, but now I'd like to build one in hopes of getting some retouching work.

Because of copyright violations, I know displaying before and after shots is out of the question (as well as asking the photographer for permission) ... and I know that even using a scan of the cover of a magazine is also violating copyrights.

I do have other samples I've been working on that would not violate any copyrights, however I feel that it would look much more impressive to be able to show where my work has been published in the media.

If you were hiring someone, and they simply said they had done "X Person for the cover of X Magazine" would you believe them and would that be enough to impress with the combination of other great samples? Is it acceptable, during an in-person interview, to bring in an actual copy of the magazine to show? Or would it be worthless without a Before to compare to?

Any thoughts and advice would be much appreciated. I want to impress, but want to be as professional and lawful as possible.

Just curious as to why you think asking a photographer for permission is so totally out of the question and against copyright laws?
Unless its specifically forbidden in your employment contract - I dont see the problem.
You should also state where you are from/working because copyright laws vary from place to place.

Have you considered tearsheets? These are just what they sound like, sheets torn from the actual magazine. You just send them along with a statement of what part of the work you did and probably a reference to someone who can verify the info. I've never tried it myself, considering I've never been published, but I've read about it.

Tearsheets does sound like a good idea!

Do you have any suggestions what I could put in my online portfolio to indicate that I have these tearsheets to show? I'm just worried that someone might not think my portfolio was that impressive without them and wouldn't call me in for an in-person interview.

Here's what I found out- if you publish scans of the magazines or whatever publication your work was in, you run a risk of copyright infringement, because that is a reproduction of someone else's work, either the photographer or a writer or any number of others who worked on the piece. When you send a tearsheet in the mail, for instance, it was actually bought and has not been reproduced, hence no copyright infringement. So, I would post your work, only the "afters" unless you have permission from the photographer for the "befores," and a client list to prove what a tearsheet would have proven- that you've been published.