The New York State Legislature, just like other state legislatures around the country, came up with an ingenious solution. They developed a series of "presumptions" that would apply whenever a gun is found in a car. These presumptions would relieve the Government of the sticky business of actually having to have direct proof that a person committed a crime.
For example, in New York, when an illegal gun is found in a car (and I mean anywhere in or on or about a car, including secret compartments in the trunk of the car) EVERY SINGLE PERSON IN THAT CAR, whether there are 2 or 202 people in the car is PRESUMED to be in possession of that gun. Every single person in that car can be indicted, brought to trial, and convicted based only on proof of the fact that the person was in the car and that the gun was in the car at the same time.
Now the New York Legislature, as well as other state legislatures realized that this business of PRESUMPTIONS when actual proof is lacking might pose a problem to those who would try to pervert our Constitution into a stumbling block to efficient justice. The New York State Legislators remembered something from 5th Grade about proof beyond a reasonable doubt and the presumption of innocence. These two lofty, technical principles represented something of an obstacle to the more pressing need to make sure that people who hide guns in cars can't get away with it by relying simply on saying, "not mine" when the gun is found under their seat.
But our legislators were a clever group of lawmakers and discovered a magic word that, as long as they used it, would trick the old fogies in our appeals courts into letting their PRESUMPTIONS stand. This magic word was "PERMISSIVE." You see they realized that if they simply said that the PRESUMPTION was PERMISSIVE and not MANDATORY, then the presumption did not run afoul of the presumption of innocence or the requirement for proof beyond a reasonable doubt.