I belong to an organization of attorneys that has a couple of conferences every year. Every conference, we have a t-shirt with some witty saying on it. I want to submit “Fighting injustice since 1974 (it’s taking longer that we thought)”, but it occurred to me that it might be copyrighted. Is it, or can I go ahead and submit it for a t-shirt?
That would be trademarked, for commercial use, not copyright. Beyond that, I’ll defer to the lawyers.
The line “fighting ignorance since 1973 (it’s taking longer than we thought)” is, of course, subject to the copyright of the Chicago Reader, or whoever first wrote that and had it “published.” You cannot copy it without violating that copyright.
But your line would not be a copy of that, since you change ignorance to injustice and 1973 to 1974. So, you would potentially be in the clear.
However, it is possible that the line is the subject of trademark protection. If that is the case, you would potentially be restricted from using it for your own commercial gain. There are exceptions, and it’s possible yours would be an exception. In this regard, I’ll exit stage left so that the IP lawyers can offer their pearls of wisdom. 
Copyrights generally don’t apply to very short works of only a few words, but I’m not sure where the cut off is (it certainly isn’t specified exactly anywhere, more a matter of what you can get away with).
Trademarks only work for the field of services they are aimed at. If you use the same one in a different field, you can be free and clear. Modified and in a different field paired together is even safer.
IANAL, but I would be surprised if something that modified from the original and being used for such a non-competing purpose would be violating trademark. Maybe you know a lawyer or two who could look it up for you?
ETA: I guess that’s a simulpost and agreement with Dan Norder’s second paragraph.
I don’t know, you’re the attorney.
Heh. Just messing with you.
No.
No.
Irrelevant.
Are you really a lawyer?
As has been noted, short phrases and slogans are not protected by copyright law. The only type of protection here that might be applicable is trademark law. Trademark protection is available under federal (statutory) law and under state (common and statutory) law.
That being said, I think it’s impossible to come to any conclusions in the context of this message board.
The key questions are:
(1) Does the Chicago Reader use the slogan as a trademark, i.e., an identifier of the source (the Chicago Reader) of goods or services (the Straight Dope newspaper column)? A subquestion here is – Do consumers recognize the slogan as identifying the Straight Dope/the Chicago Reader as the source of information? (If the slogan is only used in conjunction with the trademarks “Chicago Reader” or “The Straight Dope,” then it’s unlikely that the slogan qualifies as a trademark.)
(2) Would the use of the T-shirt slogan cause confusion? That is, when people see the T-shirt, are they going to think that you’re referring to the Chicago Reader or to the Straight Dope newspaper column? (Personally speaking, I think it’s unlikely.)
I’m sure the Chicago Reader would have it’s own take on these questions, but in the end, you’re really going to have to consult your own trademark attorney.
You might want to check out the Staff Report here – http://www.straightdope.com/mailbag/mcopyright4.htm