Obama seems to think so. Obama is currently trying to stop the execution of Humberto Leal Garcia, who was found guilty of raping and murdering a 16 year old girl. Apparently, she drove off with Garcia after a party and she was later found naked and dead by the side of the road. He came home with blood on him and his bite marks were found on the body so there doesn't seem much question as to his guilt in the matter.
Apparently, the BIG crime committed by Texas authorities was that they treated him like a US citizen and didn't tell Garcia when he was arrested that he could contact the Mexican consulate (it's not like he tried to contact the consulate and was stopped, that would be completely different). Since Garcia had been in the United States for around 20 years, coming into this country when he was 2 years old, I could see why it wasn't an automatic thing to tell him to contact the Mexican consulate. It's not like he was a tourist who did something wrong on vacation, he had been here for 20 years! Texas authorities were just treating him like anyone else who they were investigating of a crime. Given the equal protections clause of the 14th amendment, I don't see how you can argue with a straight face that he should be treated any differently.
I do realize there are some complicating factors in this case. There was an International Court of "Justice" (ICJ) ruling in 2004 that 51 Mexican nationals in US prisons were not properly told of their rights to contact the Mexican consulate upon their arrest. And by treaty we are supposed to abide by their rulings (though the states can't technically be compelled to). However, it seems to me that upholding this treaty would give unfair and unconstitutional advantages to illegal aliens as compared to US citizens as their treatment and sentencing would be held to a higher standard. If a born and bred Texan would have been executed for the same brutal rape and murder, why shouldn't Humberto Leal Garcia?