What if Hamlet were in his rightful place as king and made this pronouncement? What if the law of the land suddenly outlawed marriage? There would be no more marriage. Those that were already married would be grandfathered in, but their marriages would be a relic of the old laws.
What would people do? Would marriage disappear or would it just go underground? How deep is the compulsion to hitch up? Would underground churches spring up? Underground city halls? I would be curious to see the society without marriage. What would it look like if being single were privileged over marriage? Like, if you got a tax break for being single and health insurance and the right to live in the country you wanted to live in.
As a king, you could make this kind of grand social experiment, really see what happens, what might be the results of an entirely radical pronouncement. It’s actually surprising that kings didn’t make these sorts of rules more often.