User blog comment:AYET/An awkward situation - Rayleigh at GR12 after Luffy's departure/@comment-3425840-20121022214251

Well Kizaru did say that Rayleigh is someone who required a little more dedication than what the marines had at that point. My bet is, since he (Rayleigh) is not an active pirate, the upper class marines has his project at limbo (remember Garp ordering his men not to bother him). As the marines presumably has their hands full with active pirates they can't afford to go after a big shot like him.

I mean to capture the Dark King, at least an admiral has to be dispatched and with the troubles the marines had at the War and later the departure of Aokiji I doubt they can afford that kinda luxury.

As for not attacking Shakky's bar, I think they just don't regard it a worthy enough venture. Also Shakky is not a push over either. I think she can hold her own against anyone who ranks less than a Vice Admiral.