The MST claims land occupations are rooted in the most recent Constitution of Brazil (1988), by interpreting a passage which states that land should serve a "larger social function".
According to Article 186 of the constitution, the social function is performed when rural property simultaneously meets the following requirements:
The MST identifies what it believes to be unproductive rural land that does not meet its social function and occupies it. Upon occupation, a legal process commences to expropriate the land and grant title to the landless workers, while the owners do likewise to regain possession of it. The MST is represented in these activities by public interest legal counsel, including their own lawyers, sons and daughters of MST families, as well as organizations such as Terra de Direitos, a human rights organization of civil society co-founded by Darci Frigo, the 2001 Robert F. Kennedy Memorial Human Rights Award Laureate. Sometimes the courts require the families to leave. Other times, courts refuse the landowners' request and allow the families to stay and engage in subsistence farming until the federal agency responsible for agrarian reform, Brazil's National Institute for Colonization and Agrarian reform (INCRA), is able to determine if the occupied property is, indeed, unproductive.
For example, in August 1999, Chief Judge Rui Portanova overruled the decision of a trial court granting a landowner's petition to evict the MST off his property. The Court reasoned:
Before applying a law, the judge must consider the social aspects of the case: the law's repercussions, its legitimacy and the clash of interests in tension. The [MST] are landless workers [that] want to plant a product that feeds and enriches Brazil in this world so globalized and hungry. But Brazil turns its back. The executive deflects money to the banks. The Legislature . . . wants to make laws to forgive the debts of the large farmers. The press accuses the MST of violence. The landless, in spite of all this, have hope . . . that they can plant and harvest with their hands. For this they pray and sing. The Federal Constitution and Article 5 . . . offers interpretive space in favor of the MST. The pressure of the MST is legitimate. [I]n the terms of paragraph 23 of Article 5 of the Federal Constitution [that land shall attend it social function], I suspended [the eviction.] (Decision #70000092288, Rui Portanova, State Court of Rio Grande do Sul, Porto Alegre)
The expropriation process can take years.
Beginning in December 1980 and early 1981, over 6,000 landless families established an encampment on a portion of land located between three unproductive estates in Brazil's southern-most state of Rio Grande do Sul. The location became knows as the Encruzilhada Natalino. With the support of civil society, including the progressive branch of the Catholic Church, the families pressured the Military Government into expropriating nearby lands for the purposes of agrarian reform.
The MST was officially founded in 1984, as Brazil's Military dictatorship came to a close.
Over 90% of the MST's Coordinators, Regional, State and National, live in MST settlements or encampments. This is an important strategy of the MST and serves to maintain an ongoing and direct flow of communication between member-families and their representatives. Coordinators are aware of the realities faced by member-families and are encouraged to discuss important issues with said families. To assist with communication between Coordinators and member-families, and as an attempt to democratize the media, the MST produces the 'Jornal Sem Terra' and the 'MST Informa'.

The MST formed its education sector in Rio Grande do Sul in 1986, a year after the first national convention. [Fernandes, Barnard Mancano. The Formation of the MST in Brazil. Editora Vozes, Petropolis 2000, 78.] By 2001, about 150,000 children were enrolled in 1,200 primary and secondary schools in its settlements and camps. The schools employ 3,800 teachers, many of them MST-trained. The movement has trained 1,200 educators who run courses for 25,000 young people and adults. It trains primary-school teachers in most states, and has set up partnerships with international agencies, such as UNESCO and UNICEF, as well with the Catholic Church. It reached agreement with seven institutions of higher education in different regions to provide degree courses in education for MST teachers. [Jan Rocha and Sue Branford. Cutting the Wire: The story of the landless movement in Brasil. 2002, Latin American Bureau.]
In an issue of the magazine Veja, Brazil's largest, dated September 8, 2004, entitled "The MST's Madrassas", journalist Monica Weinberg visited two of the MST's schools in the southern state of Rio Grande do Sul. In her report, the MST is said to be "indoctrinating" children between the ages of 7 and 14. In the MST publication "Education Notebook, no. 8", one of the MST's stated goals for the children is to "develop the class conscience and revolutionary conscience". Children were also shown propaganda films, and taught that GMO products contain "poison" and told not to eat margarine for fear of containing GMO soybeans. The Brazilian government has no control over most of the schools, and they do not follow the curriculum set forth by the Ministry of Education which calls for "pluralism of ideas" and "tolerance". In the journalist's analysis, the "preaching" of Marxism in these schools is analogous to the preaching of radical Islam found in Middle-Eastern Madrassas.
Oscar Niemeyer, one of the most internationally renowned Brazilian architects, will be designing the Auditorium Building that will be part of the complex of the MST's National Florestan Fernandes School outside São Paulo.
In 2005, the MST partnered with the Federal Government of Venezuela, the State Government of Paraná, the Federal University of Paraná (UFPR), and the International Via Campesina (an organization that brings together movements involved in the struggle for land from all over the world), to establish the Latin American School of Agroecology. The school is located within an MST agrarian reform project known as the Contestado settlement. The protocol of intentions for its creation was signed in January during the V World Social Forum.
The first undergraduate course in Agroecology already has 100 students enrolled and will be administered by the UFPR. The students, who are associated with peasant farmer organizations from all over Latin America, will become agroecology technicians. The course, which will alternate periods in school with periods in the community, will last three years.
The march was held to demand – among other things – that Brazil's President Lula implement his own limited agrarian reform plan rather than spend the project’s budget on servicing the national debt [Ramos, 2005]. Several leaders of the MST met with President Lula da Silva on May 18, 2005. The leaders presented President Lula with a list of 16 demands of which included economic reform, greater public spending, and public housing. Afterwards during interviews with Reuters, many of the leaders said that they still regarded President Lula as an ally but demanded that he accelerate his promised land reforms.
The MST has also been accused of committing violence, including an accusation of responsibility for the torture and assassination of police officers; there is debate as to whether the perpetrators were MST members or not. 
In addition to occupying derelict farms and public buildings, the MST has also invaded and vandalized productive properties owned by large corporations. On March 8, 2005, the MST invaded a nursery and a research center in Barra do Ribeiro, 56 km from Porto Alegre, both owned by Aracruz Celulose. The MST members held the local guards captive while they proceeded to rip the plants from the ground. MST's president, João Pedro Stédile was reported to have said that not only the traditional landowner, but "international capital", was now the enemy.
In April 2006, the MST invaded the farm of Suzano Papel e Celulose, a large maker of paper products, in the state of Bahia, due to the farm having over 6 square kilometres devoted to eucalyptus growth.
Eucalyptus, a non-native plant, has been blamed for environmental degradation in Northeast Brazil. 
In June 2003, the MST also invaded the R&D farm of Monsanto in the state of Goiás 
As a method of pressuring the government, in 2002, the MST invaded the private farm of then-president Fernando Henrique Cardoso's sons
in the state of Minas Gerais, in a move which was widely condemned by Lula
and the members of the left-wing PT Party
The farm was damaged and looted in the occupation, despite the MST having been granted its demands for a meeting with Raul Jungmann, the Agrarian Reform minister. Damage included the destruction of two harvesters, a tractor and several pieces of furniture.
The MST members also drank the entire stock of alcoholic beverages at the farm, something they publicly apologized for later
Overall, 16 leaders of the MST were indicted for theft, vandalism, trespassing, resisting arrest and for holding others in captivity. 
The MST also repeatedly creates roadblocks, blocking highways
and railroads
In May 2006, the MST was reported to have helped the PCC, the prison-gang criminal organization which perpetrated the bloodiest assault against public establishments in the history of the state of São Paulo. Police phone tap records depict a conversation between PCC leaders describing how the MST helped the PCC in the organization of the largest prisoner's relatives protest in Brazilian history on April 18, 2005, with more than 4000 prisoners' relatives attending. The MST denied the link with a formal written statement implying the evidence was only an attempt to criminalize the movement. No proof to contest the phone tap recordings was provided.