De minimis

De minimus is the abbreviated version of the more descriptive, de minimis non curat lex ("the law cares not for small things"). That is, the big guns of official notice will not be aimed at trifling matters. That's why you (probably) don't get speeding tickets for being 2 kph over the limit or fined by the tax office for losing a receipt for $18.26.

But a word or two before anyone spreads their wings for a quick flight under the radar:

• Whilst an instance may be trifling, a pattern may not be. Heading home with a ball point is trifling—taking one home daily is pilfering. Safety breaches would attract the same attention.
• If insubordination can be reasonably inferred, it can overshadow otherwise trivial specifics.
  
• Similarly, other supposedly wilful conduct may be regarded as important beyond the specifics of a single instance on the perception of the precedent value. Such claims are often accompanied by characterisations such as, "it's the principle," "thin-edge of the wedge" or the "slippery slope."
  

Clearly this is subjective territory.

To finish the topic, Pearce and Geddes in their Statutory Interpretation in Australia point out that the principle of de minimis may also apply in regard to some restrictive terms in legislation, such as 'exclusively,' 'solely' and 'only.'

The question isn't who is going to let me;
it's who is going to stop me.
—Ayn Rand (1905-1982)