2.1. American rule
The first view tends to adopt American rule，so named because some rigorous U.S. lawmakers suggested to adopt the program. The rule advocates that the meaning of shall  
should be only limited to have a duty.

The supporters of American rule are exampled by A.Bryan.Garner – the Professor of Oxford University (Garner, 2005) and Professor Fan of Shandong Institute of Business and Technology. Professor Fan, in her the study of the usage of shall in the English translation of Civil Law, put forwards that the correct approach is to limit the usage of shall to express a person be obliged to do something while in other circumstances, shall should be replaced by more appropriate words according the context (Fan Huixi, 2011) .

2.2. ABC rule
In the late 1980s, some legislators of Australia, Britain and Canada put forward the principle. The initial letters of the three countries are A, B, C in turn, so the principle is called ABC rule. The view holds that since the meanings of shall are too many, and it is difficult to unify and standardize its usage, the legislators should abandon the use of shall and choose a much exact word to replace shall according the context, such as must, may, will, is entitled to.

The supporters of ABC rule are exampled by Michele Asprey, an Australian practicing lawyer and Mr. Chen. The two scholars strongly advocate to abandon the use of shall in the legal text. The former published Shall Must Go in the Australian Law Journal in 1992 (Asprey, 1993). The later published Get Rid of Virus in the Legal Translation - Shall in the Shanghai Science and Technology Translation in the same year (Chen Zhongshi, 1992) .
 
2.3 The principle of maintaining the status quo
The third group holds that the tradition should be continued, i.e., the situation in which one word shall has several meanings is still maintained, just as people have believed for centuries: to maintain the chastity of shall is both hopeless and unimportant.

 
Reed Dickerson, known as the father of the U.S. legal drafting, pointed out that the most important principle of legal drafting was to express consistently. He said that competent legal drafters must ensure that the same word or terms must be expressed the same meaning throughout the legal text. And legal drafters must be careful to avoid using the same word to express more than one meaning. In short, the legal drafters must express the same meaning in the same way and express different meanings in different ways (Dickerson, 1986). The view of Dickerson, regarded as the Golden Rule later, has become the cornerstone to guarantee the accuracy of the meaning in the law text.

Thus, the principle of maintaining the status quo does not solve the problem of the use of shall in violation of the golden rule in the law language.


3. Pragmatic Functions of shall, must and may
The expression of normative concept in the legislative English is pided into three levels: a strong command of the obligation norms, a weak command of the obligation norms and authorized norms. In Chinese law, it is common to use “必须” as a strong command of the obligation norms, using “应当” to express the meaning of a weak command of the obligation norms, and “可” to state authorized norms (Xie Xiaoying & Ma Yanzi, 2010).

3.1 The difference between “应当” and “必须”
(1) In semantic function, “应当” means reasonable or natural while “必须” means necessary, conclusive or inevitable through judgment or inference, and therefore “必须” expresses the meaning of can only be so and cannot be against it absolutely.

(2) In logic, “必须” is involved in the obligations that must to be done, while “应当” is involved in the obligations that should to be done.
法律英语中情态动词的语用功能及翻译技巧(2):http://www.751com.cn/yingyu/lunwen_6914.html