There are two land crossings between Saudi Arabia and Kuwait; and at each of them there is a "no man's land"; which is a land buffer between the two countries.
Anything in this land is considered in a neutral zone. There are plenty of vehicles and remnants of the Gulf War there (old tanks, etc.)
If you are denied entry into either of the countries, you have to cross over this land border; assuming you can enter either of the bordering countries.
If you are inadmissible to either of the countries, then you are held in the detention center and then subject to deportation.