Suppose an undocumented immigrant runs a red light. The cop stops him and gives him a ticket.
He goes to court and says "I do not have to ay this ticket, because I am NOT UNDER THE JURISDICTION of the US government".
So of course, because sirs is right, the judge says "You're right, you aren't, you got me there!"
How likely is this scenario?
Anyone in this country is under the jurisdiction (ie the Legal system) of its laws.
Perhaps the Ambassador of Belarus would not have to pay the fine, okay. But he is clearly a diplomat, and diplomats are exempt.
When I lived in Mexico, my friend Thierry Brachet, who despite the name and the fact that he was half Greek and half French, was a Mexican citizen. He drove an old Land Rover, and he never got a ticket for parking or driving in Mexico City, because his old Land Rover had Diplomatic Plates from the Belgian Embassy, where Thierry's brother worked.