"French law does not make any distinction between the different types of drugs. As far as French law is concerned, it's just as bad, whether you have got cannabis, cocaine or heroine.
"It doesn't distinguish, either, between personal use or trafficking. The only place that comes into play is when the sentence is handed down."
At the bottom end of the scale, culprits might be required to attend a drug awareness course or perhaps a year in prison, plus a small fine.
"On the other hand, and this might come into play in this case, the French legel system actually has a special case where, if you are caught with these drugs in a public place, then your fine gets larger and so does everything that comes with it," said Field.
"The police have been cracking down in the last five years on these types of drugs, particularly in nightclubs, so they may decide to go for the bigger one, which is the possibility of five years in prison and the much bigger fine of $NZ110,000."
French authorities are fighting a war against drugs, with cocaine use having increased 50% over the past five years.
"France recognises that it's a transit country," said Field. "A lot of these drugs come up through the Mediterranean and pass through France to be used in the Netherlands, where its traded sometimes quite freely.
"So the French authorities have come under a lot of pressure from people within community groups to crack down on these places, like high-end nightclubs, where cocaine is easily purchased."
Field also warned that Williams' arrest goes against the wholesome family image of Racing 92, which has already suffered the embarrassment of Dan Carter's drink-driving case in recent weeks.
Racing issued a statement over the weekend, suspending Williams indefinitely.