Signing statements - and Bush's innovative use of them - are important, as I insisted a while back. Dahlia Lithwick gives an excellent summary of the issues here. She also writes one of the cleanest paragraphs on how Bush's interpretation of unchecked executive power led to the endorsement of torture. Bush's signing statements are instructions to his own employees on how to obey or disobey a law. By telling the armed services that the McCain Amendment is optional, Bush is repeating the mistakes that led to such widespread torture and abuse in the first place:
Such mixed messages about torture allowed young, untrained guards to torture prisoners at Abu Ghraib. Where the rules for treatment of detainees had once been clear, the efforts of Jay Bybee and Alberto Gonzales and others in the White House telegraphed that some agencies could now follow different rules for torture; that not all torture really is torture; that sometimes the president may actually want you to torture; and that all this is largely for you to sort out on the ground. The McCain anti-torture amendment was an effort to create an absolutely clean distinction once more. Bush's signing statement obliterates that distinction and opens the door to yet more ambiguity and abuse.
And the future victims of such Bush-endorsed torture? They won't have a day in court, under President Bush's view of the law. Which means that—like all the mushrooming executive war powers—this ambiguous new torture regime will be secret and may never be tested in a courtroom at all.
This is how tyranny gets a foothold: in secret, and because we don't care enough to nip it in the bud.