It is common practice for law enforcement officers to wring confession from a suspect by torture, but no right-minded man would by this means compel, with any hope of success, an unwilling witness to tell the court what he did not know or what he did not want to say. As the saying goes, although the simile is not exactly parallel, you could lead a horse to the water but you could not make him drink. A man could be forced to make an extrajudicial statement against a defendant but there would be no assurance that he would stick to that statement in court, which is what counts. [People Of The Philippines V. Elizaga, G.R. No. L-2487, May 18, 1950]
Idiomatic Expression Meaning: means that you can give someone an opportunity but not force them to take it.