In Washington March 11, U.S.Senate lawmakers heard testimony about the problem from top law enforcement officials.

VOA: standard.2010.03.11

Or enforcement is the case, enforcement is the problem, but it's not the answer.

或者说，我们的确在实施它，但这种强制性的实施并非解决办法。

普林斯顿公开课 - 人性课程节选

All right, so it might be that again, the problem with enforcement, although actually in 1880 America, it's not clear that they couldn't have enforced that contract.

好的,但是我刚才说了强制性的问题,虽然说那是1880年的美国,当时这种合同是否违法没有明确的界定

耶鲁公开课 - 博弈论课程节选