Legal Question in Constitutional Law in Virginia

Yes, unless you're working pursuant to an enforceable contract

which protects you from summary discharge for this particular activity

(unlikely) which presumably is within the scope of your employment

if you're using your vehicle to deliver Domino pizzas.

However, even if you were not using your vehicle in the above-described

manner, the company could likely still fire you without penalty since Virginia is a so-called employment at will jurisdiction where an employee can be fired for nearly any reason that doesn't violate federal /state anti-discrimination laws or even for no reason at all.