You do realize how ridiculous that sounds, right? Alcohol used to be illegal in the United States, should Bill Tilden have been banned for a year because he had a beer?
Laws change, they aren't representative of cheating. The spirit of the law is what needs to be upheld; preventing cheating and unfair advantages over your opponents -- doing a line of coke so you can get some Miami poontang qualifies as neither.
Today, it should be dealt with straight away.
Any illegal drugs should result in a ban straight away, no matter how the drug is taken, unless of course they need a drug to help a condition they have which is very unlikely.