[M2Ys4U]

>I'm actually very curious now what led you to the line of thinking that it isn't possible?

The public domain is the set of all works in which no copyright subsists. Copyright automatically subsists in a work from its creation until it expires. Copyright is a property right. All property must have an owner.

Therefore a work cannot enter the public domain unless the copyright subsisting in it has expired.

(This is from the perspective of the law of England and Wales, at least. Other jurisdictions have similar legal axioms that produce the same result, though)