One Nation Under God license plates

The News2Know blog linked to an article on how Ohioans may get One Nation Under God specialty license plates.

One poster at the News2Know blog raised the question of the legal challenges they may face if Kansans were given that option. My view: "The phrase is currently a constitutional part of our Pledge. Of course, that wouldn't stop someone from suing. The question would be, 'Why would a phrase that is a constitutional part of the Pledge be unconstitutional when printed on a license plate?'"

Thoughts?