 Thirdly, the legal context of an expression may be very different from other contexts of its use. Principles of legal interpretation (for example, a legal requirement that vague criminal enactments are to be interpreted as applying only in clear cases) may make the legal effect of the use of a word more precise than its ordinary effect. The interpretation of a legal prohibition on careless driving demands an understanding of what counts as careless for the purposes of the law. The effect of a vague legal prohibition may be governed by precedents that rule out decisions that would otherwise be a reasonable application of the vague language. Even apart from the regulatory role of precedent, a good advocate or judge may have a relatively clear sense of the accepted practice in applying the prohibition, and the practice may well involve not treating certain forms of conduct as careless, when it would be fair enough, apart from that practice, to call them careless.