rental car without license tags?

What is the name of your state? MD

Don't mean if this question is not part of auto accident but I saw a car on the street today that doenst have license tags on the front or back. It looks like a new car but it doenst even have the temp tags. I'm sure it's not "legal" to drive around with no tags, but could there be an exception?

Not legal. But also none of your business!

Anything in the windows?

Several states have temporary/transfer tags that are just taped to the rear window.