Do semiclassical GR and charge quantisation imply magnetic monopoles?

Assuming charge quantisation and semiclassical gravity, would the absence of magnetically charged black holes lead to a violation of locality, or some other inconsistency? If so, how?

Yes, magnetic monopoles are theoretically expectected to exist and to be quantized due to the electro-magnetic duality, which is an example of a strong-weak or S-duality. The relationship between magnetic an electric charges, discovered by Dirac, is $me = 2\pi n$. This means that if electric charges exist, magnetic charges m are quantized in units of $2\pi / e$. – Dilaton Apr 5 '13 at 21:47