Lawsuits are expensive, even for companies that have lawyers on retainer or staff.
Allocation of the copyright between the parties will be largely a matter of contract law. If you write as a free-lancer, the rights purchased by the newspaper will depend on your particular agreement. If yous simply write a letter to the editor or contribute an op-ed piece, there may be no written agreement, and no sale of the writing. Here we enter the realm of implied agreements. As you can see the copyright bundle can be sliced very thin.