How would the existence of a magnetic monopole require the removal of world line from spacetime?

I was studying Lienard-Wiechert Potentials from Griffiths, where he wrote that electric charges cannot travel at the speed of light. Which led me to a rabbit hole of charges both magnetic and electric, wherein I stumbled upon the fact that the sheer existence of monopoles would require the removal of worldline from spacetime. Even after quite a bit of research, I couldn’t understand what that meant and also how would they modify general relativity?