U.S. varies by state.
Possession of marijuana is a misdemeanor in California for one ounce
(28.5 gms) or less and punishable by a maximum $100 fine.
Florida already has the dubious honor of having the nation's harshest marijuana
possession laws — less than 20 grams can land you in jail for a year and cost you
$1,000. Even worse, possession of more than 20 grams is a felony.
If you do luck out and get a misdemeanor possession in Florida be careful for the
next offense is a felony.
Florida 3 strikes law plays well with crack and mary jane.

So, depending on the state you are in it may be a ticket or very serious offense.