Yes, this is all legal. However, legally, the commissars of the Soviet Union also had the right and the power to ban ideas, books, works of art, and every form of expression.
The problem is the result: a small elite group of cultural commissars controlling the flow of ideas, and shutting undesirable ideas out of the public discourse and the public mind.
That is how totalitarian regimes are created and maintained.
Incidentally, the "government force" in copyright protection is the protection of copyright. That was done for the explicit purpose of fostering the publication of works, since the American lawmakers could never imagine that there will come a time in which huge corporations will ban books on political grounds.
All the government has to do is to stop enforcing copyright protection for copyright-owners who no longer publish the copyrighted works. Guaranteed other publishers will pick up these Dr. Seuss books, since he is by far the most popular children's books author of our time.
As things stand, bid these books adieu. Your children will not be able to read them.