Is there a prostitution problem? And what is the prostitution problem?
Is it the problem that prostitution is sinful? Then they could perhaps finally come to the 21st century, and the problem is solved by itself.
Is the problem that prostitution is illegal? That's a self imposed problem, they can just change the law (like other countries and some states/counties have).
Is the problem that society has decided it shouldn't have prostitution? That's valid, I guess, but they should ask to verify whether this is true, before considering it a problem (and before making laws unilaterally. E.g. society apparently didn't consider marijuana to be as much of a problem as lawmakers made it).
Is the problem that prostitution is a dangerous and coercive environment? This stems from it being illegal, and thus unregulated.