Josh Gerstein at Politico flags a pretty dubious argument (see also here) against seeking the death penalty for the alleged 9/11 plotters: They're being tried in New York, which doesn't currently have a death penalty statute, so doesn't it offend federalism for federal prosecutors to seek the death penalty there?
No, it doesn't. As a strictly legal matter, federal criminal law and state criminal law are entirely separate bodies of law; a state government (formally, at least) does not control or influence federal prosecutions within its jurisdiction. And as a theoretical matter, the whole point is that a federal crime isn't just a crime against the citizens of the state in which it was committed; it's a crime against the people of the United States. Montanans and Tennesseeans have just as strong an interest as New Yorkers in determining what the punishment should be for federal crimes committed in New York.
That's not to say there aren't federalism concerns implicated here. There certainly are--just not in this particular case. In contrasting the case of the 9/11 hijackers with a Bush-era death penalty prosecution in Vermont (another non-death-penalty state) that angered some liberals, Gerstein notes:
Critics complained that Ashcroft was pursuing the death penalty over the objection of local U.S. attorneys and in cases where there was no particular federal interest. In the 9/11 case, prosecutors appear to be on board and the national quality of the crimes is evident.
Think about the implications of that for a minute. Under what confused theory of federal-state relations is it acceptable for the federal government to prosecute crimes where there's "no particular federal interest," as long as the feds don't impose the death penalty? The offense to federalism is the fact of federal involvement in such cases, not the punishment sought. The federalization of criminal law is a huge problem--there are lots of federal crimes, especially involving drugs and guns, that shouldn't be federal crimes at all. But when there is a federal interest, as there obviously is in the 9/11 case, the state's concerns need to take a backseat. Federalism isn't about simply deferring to state preferences; it's about keeping the federal government out of state affairs and, equally important, about keeping the states out of federal affairs.
It's not that the federalization of criminal law isn't without benefits. I worked at a U.S. Attorney's Office last summer, and it feels pretty awesome to be able to deploy the resources of the federal government to go after miscellaneous malefactors threatening the public. (And states with overburdened law-enforcement and criminal-justice systems, like California, are often all too eager for the help.) But there's no justification for forcing the citizens of state A to pay taxes to protect citizens of state B from local harms that they aren't willing to tax themselves to be protected from. And, somehow, making assistant U.S. attorneys (and summer law-student interns!) feel like their jobs are awesome doesn't really strike me as a great rationale for expanding the reach of federal criminal law.