God doesn't allows polygamy, David and Solomon where punished by God because they were polygamous, it's not allowed by God, David and Solomon used their powers as kings to practice polygamy, as kings they can easily get wives.
God doesn't allows polygamy and that was why they were punished by God.
Davids lost his child, who was a fruit of fornication, and God was angry at Solomon because of he practiced polygamy.
Polygamy isn't allowed by God, men can decide it for themselves, because we have the power to decide.
GOD PRESCRIBES AND MAN DECIDES.
To obey to disobey all depends on our decision, upon your decision you would be answerable to God, if you did something evil you will be answerable to God.