Legal definition and rules governing on jams ⎯
FDA definations
The U.S. Food and Drug Administration (FDA) published standards of identity in 21 CFR 150, and treats jam and preserves as synonymous, but distinguishes jelly from jams and preserves. All of these are cooked and pectin-gelled fruit products, but jellies are based entirely on fruit juice or other liquids, while jams and preserves are gelled fruit that may include the seeds and pulp. The United States Department of Agriculture offers grading service based on these standards.
Canadian regulations
Under the Processed Products Regulations (C.R.C., c. 291), jams, jellies, citrus marmalade and preserves are defined. Each must contain a minimum percentage of the named fruit and a minimum percentage of water-soluble solids. Jams “shall be the product made by boiling fruit, fruit pulp or canned fruit to a suitable consistency with water and a sweetening ingredient", jellies “shall be the product made by boiling fruit juice or concentrated fruit juice that is free from seeds and pulp with water and a sweetening ingredient until it acquires a gelatinous consistency."
European Union directives on jam
In the European Union, the jam directive (Council Directive 79/693/EEC, 24 July 1979) set minimum standards for the amount of “fruit" in jam, but the definition of fruit was expanded to take account of several unusual kinds of jam made in the EU. For this purpose, “fruit" is considered to include fruits that are not usually treated in a culinary sense as fruits, such as tomatoes, cucumbers, and pumpkins; fruits that are not normally made into jams; and vegetables that are sometimes made into jams, such as: rhubarb, carrots, and sweet potatoes. This definition continues to apply in the new directive, Council Directive 2001/113/EC of 20 December 2001 relating to fruit jams, jellies and marmalades and sweetened chestnut purée intended for human consumption.
Extra jam is subject to somewhat stricter rules that set higher standards for the minimum fruit content (45% instead of 35% as a general rule, but lower for some fruits such as redcurrants and blackcurrants), as well specifying as the use of unconcentrated fruit pulp, and forbidding the mixture of certain fruits and vegetables with others.
Reference: http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31979L0693:EN:NOT, Wikipedia