Rep. Tom Tancredo has introduced H.R. 6975 (link), a very short bill that would amend the Immigration and Nationality Act to say:

(G) SHARIA LAW SYSTEM- Any alien who fails to attest, in accordance with procedures specified by the Secretary of Homeland Security, that the alien will not advocate installing a Sharia law system in the United States is inadmissible.

I'm mostly all for it, and for a lot of similar things. While we certainly want to avoid requiring loyalty oaths of those who are already citizens, there's no reason we should admit those who don't buy in to our fundamental concepts, whether Constitutional or, in the case of Aztlan, our terroritorial claims.

Needless to say, the usual suspects won't like it, and one of those is Jim Harper from the Cato Institute, a supposed libertarian group with some interesting funders and which has put forth some odiously anti- and un-American ideas. Says Harper (cato-at-liberty.org/2008/09/20/fear-of-sharia-oh-please):

But more importantly, a law like this communicates precisely the wrong thing to new immigrants and the world at large. It tells the world that we’re a weak, fearful country, and that we believe Sharia law is possible in the United States. It tells the world that we’ve come off our traditional moorings and that we no longer believe in free speech and tolerance of all opinions, no matter how wrong.

Unfortunately, we have to a certain extent come off our "traditional moorings", both because of those who put money before fundamental American concepts (see Cato) and because of those on the far-left who've been mainstreamed (see the ACLU, etc.) And, of course, Sharia law barely failed in Canada but is apparently now part of England's laws.

Why take the risk just to prove something?

However, Harper is willing to make a guarantee:

There is no possibility — none — that Sharia law will be established in the United States. Not by any government body at any level.

Of course, his guarantee means nothing; if he's wrong would anyone notice? If anyone did, he'd probably just say he was wrong or just move somewhere else. It's better to be safe than sorry, and a guarantee from Harper is worthless.