Originally Posted by whitearrow

I would have to disagree. You may not have been admitted yet, but you are certainly on the territorial soil of the US, not on Canada's or Mexico's or wherever you came from. If you started snorting cocaine while waiting in line, and were arrested, you would be protected by the US Constitution, despite your lack of formal admission. Among the many other legal issues that would arise if you weren't in US territory at the time, the LEO's would have no jurisdiction to arrest you. The government can't have it both ways.