The Laplace Dirichlet problem

\[ \Delta u = 0 \text{ in } \Omega, \quad u = g \text{ on } \partial \Omega \]

is solvable for every \(g \in C^0(\partial \Omega)\) if and only if all \(x \in \partial \Omega\) are regular .

Proof
If all points are regular the solution is given by the Perron solution . Otherwise a solution for \(g = |x - x_0|^2\) is a barrier for \(x_0 \in \partial \Omega\). To see this, one should start with path-connected domains and proceed with path-connected components.