French for "Let the good times roll." It's a common expression in Louisiana (not in France), though it's almost always spelled incorrectly. This is the one and only correct spelling of the expression, in either Cajun French or Parisian French. Sadly, even reputable institutions like the Audubon Zoo and the New Orleans Ironman 70.3 use variations of incorrect phonetic spellings they find online.
Laissez les bons temps rouler!" is a Cajun expression meaning "Let the good times roll!" It strongly conveys the "joie de vivre" ("joy of living") attitude that pervades south Louisiana. It is mostly associated with New Orleans. (THE BEST CITY IN THE WORLD!)
An economy or market with no regulation or restrictions on how the said market operates, thus allowing the most efficient allocation of a resources in an economy. The laissez-faire or 'market system' is the unplanned capitalisteconomic system. The extreme opposite is N.Korea, Cuba, China etc.
The 'passive' approach, or that of non-intervention to Macroeconomic management (as stated by harry flashman) is just one feature of the laissez-faire or market system.