Nearly every summary of creationism and the law that I've read includes some sort of statement to the effect that 'the judicial decisions have left the door cracked slightly open for creation science.' Two generally excellent books on the subject illustrate this phenomenon.

Edward Humes, in Monkey Girl writes about the 1987 Edwards v. Aguillard Supreme Court decision striking down a Louisiana law requiring that "creation science" be taught. Humes quotes Scalia's rather juvenile dissent (the man couldn't help but drape his argument in insults for his colleagues), and writes:

In other words, Scalia was sending a signal. Someday, if the stars realigned and a more conservative court membership took the reins, he would revisit the logic behind Edwards, which he derided as "Scopes-in-reverse."

Edward Larson, in his definitive legal history of Creationism Trial and Error, wrote that even the majority in the Edwards case left the door open a crack:

Brennan leavened this sweeping repudiation of creationism laws with a measure of accommodation to those sincerely interested in teaching creationist scientific concepts... Only time will tell how wide a door this opened.

For supporters of good science education, this language sounds worrisome. But in all honesty, the door is wide open. If Intelligent Design really were science, there would be no reason to bar it from the classroom. If creationists want to teach their ideas in science class, all they have to do is produce successful science - which I predict they will never, ever do. As it stands, the Intelligent Design people never bother to come up with testable hypothesis or propose (much less execute!) experiments or field studies.  The oft-repeated claim that they can't do science because mainstream scientists don't give them a chance is a feint - the Discovery Institute, the institutional  home of Intelligent Design, has enough money to fund research on the scale of a typical university, National Science Foundation-funded lab. Nobody is stopping them from doing science.

In his dissent in Edwards, Scalia's main argument wasn't so scary - he argued that there should have been a trial to determine whether or not "creation science" was science or just religious ideology. (The Supreme Court upheld a lower court ruling rendering judgment on the case without trial.) I don't find that so worrisome, because every time creationism does go to trial, it loses, most recently in federal court in Harrisburg, PA. Judge Jones, a Republican, Bush-appointed judge basically took Scalia up on his challenge and let Intelligent Design have its day in court. Intelligent Design failed spectacularly, just like its Creation Science predecessor did in Arkansas 23 years earlier.

What this suggests is that, in spite of people's worries over Scalia's Edwards dissent, the creationism issue (unlike say, Roe v. Wade) is not something that desperately depends on how many liberal judges there are compared to conservative ones. Over and over again in the last 30 years or so, the issue of creationism is not that complicated when it comes to the First Amendment.

The door for teaching scientific alternatives to evolution is wide open, but the price of entry is good science. I'm betting that's a price too steep for intelligent design to ever pay.