if there are limitations, how do they enforce them?
Right now the limit is 0 at most stores since they don't have any. Check for availability
<http://iphoneincanada.ca/forums/forumdisplay.php?2-General-iPhone-Discussion>
before your trip. Bring a SIM card, so you can be sure to get one that is unlocked. There have been some mistakes.
<http://iphoneincanada.ca/forums/showthread.php?9300-Check-your-receipt-if-you-b ought-it-Unlocked!>
and just one thing, buying an iPhone in American! Apple store (for full retail price of course), I heard you still have to sign some data plans? or can I, european, walk in fifth avenue store in NYC and buy 10 iphones without any kind of contracts? (I know they would be locked, but that isnt really a problem anymore.)
It may not be a problem now, but may become one if you ever update the iPhone. Also newer iPhones will be sold with newer firmware that may not be unlockable.