yes

a Green Lantern can create anything if they have enough willpower.

Seeing as how DC Comics Presents #26  was 30 years ago (pre-Crisis), do you still think that's an ability the Green Lanterns have today?  And if it is, one would wonder why they're able to imitate the effects of kryptonite.

" Seeing as how DC Comics Presents #26  was 30 years ago (pre-Crisis), do you still think that's an ability the Green Lanterns have today?  And if it is, one would wonder why they're able to imitate the effects of kryptonite. "

eh, knowing the Guardians, there's probably an ulterior motive in there somewhere.

I didnt know they could do that

makes sense. all theyre doing is creating a mineral that exists in their universe.
not tough for a Lantern.

One of the signature abilities of the GL ring is the ability to simulate any form of energy, from the fundamental forces of electromagnetism and gravity, to the common forms of heat and electricity, to the exotic forms of hard light and concussive energy, to the traditional energies of the electromagnetic spectrum.
 
That includes simulating Kryptonite radiation. The versility of the Power Rings are immense. There's a reason they're considered to arguably be the greatest weapon in the universe.

yes they can and it doesnt matter!  GL fans dont go thinking they have a chance against superman ..........a thought based weapon against a guy whos 200 times faster than a thought! BAM! case closed.

" yes they can and it doesnt matter!  GL fans dont go thinking they have a chance against superman ..........a thought based weapon against a guy whos 200 times faster than a thought! BAM! case closed. "

"
    "

As far as I know they have never specifically said that the CL Corps rings don't have the ability to create kryptonite.  Even if they can't Alan Scott's ring can.

" Seeing as how DC Comics Presents #26  was 30 years ago (pre-Crisis), do you still think that's an ability the Green Lanterns have today?  And if it is, one would wonder why they're able to imitate the effects of kryptonite. "

Since it's possible for a GL to create green K, shouldn't they be able to create anything which would technically in a way make them able to twart off anyone just about?

interesting I never knew that they could duplicate kryptonite radiation but is it as strong as the real thing or is it weaker ?

So if A Green Lantern can create Kryptonite, can a Sinestro Lantern create yellow sunlight?

Here's my two cents: A Green Lantern ring creates constructs made of green ENERGY, not matter-based items; therefore the rings should not be able to synthesize actual kryptonite... however (as referenced in other posts) the rings, being receptacles of energy, and the most powerful weapons in the universe, should by all accounts be capable of replicating the unique and specific energy signature of kryptonite, assuming the ring and the bearer have knowledge of what the properties of kryptonite radiation actually are. 
 
Kyle Rayner did this in a Superman story from back in 1998, I believe, although I never had the chance to read the conclusion of that story. 
 
Being that the rings are so powerful, I theorize that an accomplished Green Lantern may, with enough skill and willpower (and knowledge of complex nuclear physics!!!), be able to use the ring's power to alter the sub-atomic structure of any matter and turn it into any other kind of matter they so desire; such as rocks into gold, or steel into kryptonite etc. but this would take some time to master, possibly. But, hey, if Firestorm can do it....!
 
In a Green Lantern story from about 2002, Kyle mentioned that he could split atoms with his ring. 
 
I also theorize that throughout the publication of these kinds of stories, many writers and fans ASSUME that Green Lanterns can easily create kryptonite simply because it's green and so is the power of the ring, but this then just becomes a plot device to bring the two characters together for a good old mash-up. Remember, Green Lantern rings create ENERGY constructs, not MATTER. 
 
Side note: Superman may well have the advantage in a fight... In JLA: The Nail, Hal Jordan was easily wounded in a battle with Bizarro drones. In Superman: Red Son, even a team of Green Lanterns were no match for the "faster-than-thought" Superman. Still doesn't explain how, during the Sinestro Corps War, Superboy-Prime was able to so easily trounce new Ion Sodam Yat, who has a Green Lantern ring AND has the power of Ion AND is a Daxamite with the same powers as Kryptonians..!!!

Can they still can?

So if A Green Lantern can create Kryptonite, can a Sinestro Lantern create yellow sunlight?

@ComicCrazy: Yeah same here

@Dane said:

a Green Lantern can create anything if they have enough willpower.

Does this mean that they can create food? I assume the moment they stop concentrating, it disappears, but is it technically possible to create, eat, and digest GL-made food, as long as the Lantern keeps his concentration throughout the process?

The nail and Red Son are both Elseworlds so they don't count, and Green Lanterns can still have shields to increase their durability as well as using the energy itself to make their bodies stronger. As for SBP vs Sodam Yat, Sodam is just a Daxamite ( Diet Kryptonian), had just gotten his powers and therefore had no idea what it was he could do, and was also a complete arrogant bastard that thought it smart to just fist fight Prime for the most part instead of using everything in his arsenal. Prime also impaled him with lead reactor rods and lead is to Daxamites like Kryptonite is to Kryptonians except they are perma-screwed after exposure, furthering their stats as D.K.'s.

yes.
BB

I thought they lost that power

@darkningdawn said:

I think you answered you're own question...

@g_mort: Sry, but wouldn't the RING need knowledge of nuclear physics? The Lanerns make guns and planes and stuff without understanding them, and I'm sure none of Earth's lanterns are physicists who know the intricacies of electromagnetism or thermodynamics well enough to replicate them. Also, the ring would only need to know enough about kryptonians to SIMULATE kryptonite irradiation; there's no need to actually use the exact wavelengths emitted by the rock -- considering that high-end (well, middle-of-the-line for comics) Earth science can duplicate kryptonite after enough scanning, I see no reason for the Guardians (or the rings they made) not to be cable to cook up something just as effective on-the-spot -- especially since they probably have enough records to figure out how kryptonium became krptonite (assuming that's still the current theory; I haven't kept up with comics much since "New 52")

@Omega Ray Jay said:

I didnt know they could do that

Wow

Of course Green Lanterns can replicate Kryptonite. They've done it pre-crisis, and done similar enough things post crisis.

if you're talking about The Last Will and Testament of Hal Jordan than it probably isnt. shame though. it was one of Hal's best stories.