My sister’s estranged husband is stalking her

Dear Harold,

My elder sister’s marriage was embroiled in several family disputes before it finally hit the rocks and ended up with a separation in court. However, her separated husband has refused to let go and has been a constant bother to her. For instance, he walks into her house unannounced when drunk and demands to see the children during school days despite court directives setting specific timelines on when the children can go to his place – alternate weekends. He also wants my sister to move back in with him, which she is against. Is there a way that my sister can stop his advances and unbecoming behaviour in contempt of court directives?