What I mean is, if let's say www.lexluthor.com wasn't used, would I be legally allowed to use it even though the name "lexluthor" is copyrighted by DC Comics?
Well I guess the trademark would be enforced in america. For example, if I made website about NFL football and called my website www.All-About-NFL-football.com would that be legal? or could they kick me off my domain?
they could take it from you for using their NFL mark if you put anything to do with football. Could and would are very different though, some companies are far mroe aggressive than others. For instance, many companies let people use their TM for fansite/communities and whatnot without issue. Others don't want you using their mark in any domain and will c&d anything that has it with no regard for legitimate names and uses (ie if ford sued me for owning afford.com)
This is definitely a trademark issue and not copyright. Names cannot be copyrighted in the US, even if fictional. There are a number of legal "fair-use" reasons that you can use a trademark. This applies to domain names as well, but as domain names are so short it is harder to meet the fair-use doctrine. Besides not being able to use the trademark for monetary purposes (that always applies to having paid membership but does not always apply to ads), you must make it clear that the use of the tm is not linked with the tm holder. Examples: tm.com (like your lexluthor.com) - infringement as using just the tm is likely to cause confusion tmsucks.com - not infringement as it is pretty clear that this is not linked to the tm holder buytm.com - probably infringement tmreview.com - could go either way depending on several factors Those are just some of the issues when looking at just the domain itself. If a domain name survives the initial stage of an infringement dispute, then there are several other factors that are looked at (including other domains that you hold, content on the site, etc....) Generally, it will just be easier not to bother with such a domain.
Is it? I'd love to hear what you're going to back up your statement with. "Illegal" does sound too strong here I think.
There is no problem with illegal, as trademark is governed by laws and breaking laws is illegal. I take issue with the word strictly. That would suggest that it is always illegal. However, there are a number of ways that a trademark can be legally used by people other than those that own it. In addition, it is possible for there to be multiple trademark registrations for the same phrase in different industries.