So that not one person is given so much power they can attack the rights of citizens.
        
             
        
        
        
The Open Door policy was a statement of principles initiated by the United States in 1899 and 1900. It called for protection of equal privileges for all countries trading with China and for the support of Chinese territorial and administrative integrity.
hope this helps :)
 
        
                    
             
        
        
        
Definition:
Common law is a body of unwritten laws based on legal precedents established by the courts. Common law influences the decision-making process in unusual cases where the outcome cannot be determined based on existing statutes or written rules of law.