The persistent anomalies in a variety of rare b->sll decays are one of the most intriguing signs of BSM physics at the moment. The scalar leptoquark S3 is a common model proposed to explain these anomalies but it has some conceptual difficulties which are often brushed over, relating to proton decay and the generic lepton coupling.
After giving a general introduction to the history and current status of the b->sll flavour anomalies, I will discuss these problems and how promoting one of the accidental global symmetries of the SM, L_mu - L_tau, to a gauge symmetry can provide a nice solution to these problems. I also discuss the naturalness of introducing new scalars above the EW scale and will use an argument known as finite naturalness to justify the existence of a mass hierarchy.
