[Boogieman]

“Then why is it not illegal for a police drug dog to sniff your car?”

Because the car is on public property, and nobody requires a warrant to walk around on public property, drug dog or no.

[South40]

Because the car is on public property, and nobody requires a warrant to walk around on public property, drug dog or no.

Americans' search and seizure rights should not end when they enter public property.

[Lurking Libertarian]

See the link in this post.