THE WEEK IN REVIEW: Monday, November 7, 1994 to Friday, November 11, 1994 TUESDAY, November 8, 1994 - The Financial Post, November 12, 1994 Canada's lax currency laws allow billions of dollars to be laundered here annually and interfere with international investigations, one of the world's top Mafia fighters said. Canada has ''at least 10 organized-crime groups but . . . there is no law that targets organized crime, as there is both in Italy and the U.S.,'' Italian prosecutor Nicola Gratteri told a Toronto symposium on the global Mafia. Antonio Nicaso, an organized crime specialist and the writer of several books, told the audience Canada is the ''underworld laboratory for organized crime.''