From Longman Dictionary of Contemporary Englishthe long arm of somebody/somethingthe long arm of somebody/somethingwritten the power of someone or something that has authority, especially to catch and punish someone He won’t escape the long arm of the law. → long
Examples from the Corpus
the long arm of somebody/something• Roy tries an overhead pass, but the long arm of a Stanford player plucks it out of the air.• How far are you prepared to stretch the long arm of coincidence?• The old woman has turned into the long arm of her family.• Oct-11a is located in a region of mouse chromosome 9 homologous with the long arm of human chromosome 11.• I managed two months at large before I felt the long arm of the law on my shoulder once again. 