Typo in my Passport?

Some of you who know me know that i am sometimes an obnoxious grammar snob. If you read much of this or listen to me talk, you know that it's fairly ridiculous for me to be a grammar snob because i really don't know that much about grammar! There are some things that bother me though, because i'm just that way; what can i say?

So i was looking at my passport and i think i see a grammatical error. One word that almost never seems to get used when it should is "ensure." The word "insure" almost always gets used instead.

Look at the picture. I think it should say "ensure", not "insure". What do you think?

Really though, it can't be an error can it? Isn't that the text of the constitution. Now I have to go look it up...
...ok, i'm back. Yeah, that's it. So i guess I don't understand the difference between the two words either. I thought Insurance pretty much referred to financial institution type of references, and Ensure meant to make sure of something. I dunno... English is hard.

Also, feel free to correct my grammar with extreme prejudice and complete lack of mercy. In fact, that goes for all my posts really. I don't mind, and maybe if i'm corrected enough i'll get it right.