Alternative to a warning splash page
 

As an alternative to a warning splash page (which many surfers find annoying), would this be an alternative?

What if you place this in your Terms & Conditions/Term of use link:

"By using this site, you agree to the Terms & Conditions which states that you must be at least 18 or 21 years of age (according to your community standards)"

Would this be legit?

I don't know much about that side of the law, but how does this give a surfer warning that doesn't want to view porn?