Wiktionary
run afoul of
vb. 1 (context nautical English) To become entangled in; to run aground on. 2 (context idiomatic English) To contravene
Usage examples of "run afoul of".
To a man, they wore the red badges of Amefel, having no wish to run afoul of their own watchers in the hills.
So he halted his ox and stared down into the furrow, thinking that perhaps he had run afoul of some nether root.
She stepped carefully, so as not to run afoul of the hobble and trip and fall.
He could afford to skate no faster than he could see, lest he run afoul of a broken hump or even a break in the ice.