Freedom of assembly is the freedom to associate with, or organize any groups, gatherings, clubs, or organizations that one wishes. It is explicitly guaranteed in the First Amendment to the Constitution of the United States, as well as the Canadian Charter of Rights and Freedoms which is constituted as Part I of the Constitution of Canada of 1982.
In countries without freedom of assembly, certain political parties or groups may be banned, with harsh penalties for any members. Public protests against the government are usually banned as well.
This makes freedom of assembly closely linked with notions of freedom of speech. Thus, while one can be allowed to advocate the murder of the President, one is not necessarily allowed to be a member of a group that seeks to achieve this goal.
The freedom of assembly in order to protest sometimes conflicts with laws intended to protect public safety, even in democratic countries: in many cities, the police are authorized by law to disperse any crowd (including a crowd of political protesters) which threatens public safety, or which the police cannot control. The idea is to prevent rioting. Often local law requires that a permit must be obtained in advance by protest organizers if a protest march is anticipated; the permit application can be denied. Sometimes this bureaucratic power is abused by lawmakers if the protest is not a popular one in the community or with the local government, with the permit process in some cities taking a great deal of time, organization, and even money required before a permit is issued -- and then, when issued, time and location restrictions are sometimes added.
From time to time, local permit laws collide in court with the freedoms of assembly and of speech, such as in February 2003 when protests were anticipated over the exclusion of women from membership at the Augusta National Golf Club where golf's Masters Tournament is played every year. The Richmond County, Georgia county commission implemented a new rule requiring 20 days of advance notice before a protest, and giving the county sheriff the power to approve or deny permits, and to dictate the location of demonstrations. The sheriff turned down a permit to protest in front of the golf club but approved a protest half a mile away. Two courts upheld the ordinance granting the sheriff this power.