There is no ambiguity. It simply requires enough wisdom to read and consider the full context rather that conveniently snipping verses to make an incomplete narrative.No, polyginy (polygamy is technically an incorrect term) is regulated by the deity of the bible... if you believe the bible to be the word of God. The same with slavery. Rules are presented, but the practice is never prohibited/banned/declared a "sin".
It makes no rational sense that the bible deity would be ready to call something a sin without any ambiguity, but then get cold feet about calling another action a sin.
Genesis 2:24 lays the foundation declaring a man CLEAVE to his wife and become ONE. This principle is repeated throughout the bible. (Deuteronomy 17:14, 17) (1 Timothy 3:2) (1 Timothy 3:2-12) (Ephesians 5:31) (1 Corinthians 7:2) (Mark 10:7)
The Bible makes no apologies for the fallibility of man...that's the POINT....to highlight the sinfulness and disobedience of man and to highlight CONSEQUENCES illustrating man's need for a savior. Rather than promoting polygamy, the examples of polygamy in the bible include detail regarding the consequences to individuals, family and society.
As for "regulation"...regulations shouldnt be seen as promoting or condoning the behavior. Much like the cultural acknowledgement of slavery, indentured servitude, it simply recognizes that man was created with free will, and within the context of society turning from God and reaping what it sows, provide some degree of protection to those involved. (Note that virtually all of these 'regulations' come from man in Mosaic Law...not from God directly.)