In addition to illustrating the principle of freedom of contract and its manifestation by focusing on the legal restrictions,including the bodies of the contract,the expression of the parties,the responsibility of violating contracts,the effect of contracts and so on,this essay also gives it an objective value judgment.

The legal limits of police shooting shall follow the principle of proportionality and meet the requirements of appropriateness,necessity and balance.

Historically, the doctrine of absolute freedom, doctrine of restricting behavior and doctrine of restricting interests are the main doctrines of legal limits of academic freedom.

According to the public interest principle,the lest limitation principle,the afterwards limits principle,the clear and present danger principle,the specially measures principle,and the clear legal rule and limit precise principle,this paper proposes the legal limits of the freedom of speech on the internet.