In 1980, 13 members of Parliament published a letter criticising Mobutu's regime and were arrested for "aggravated treason".
Lihau testified on their behalf during the ensuing trial.
Two years later he joined them in founding the Union pour la Démocratie et le Progrès Social (UDPS) as an opposition party to Mobutu; Lihau soon became the new party's president.
Mobutu was particularly disturbed by Lihau's membership in the party since, as a native of Équateur Province, he added to the geographic diversity of the organisation and therefore its political clout.
In retaliation, Mobutu incarcerated him, suspended his rights, confiscated his personal property, and eventually banished him to the village of Yamake in Équateur Province.
In August 1983 Lihau joined several of his colleagues in attempting to interrupt a meeting between government officials and United States Congressmen at the Hotel InterContinental in Kinshasa while wearing Western suits and ties (then banned by Mobutu).
A violent struggle between the UDPS members and Mobutu's security police ensued in full view of the American delegation and received a great amount of media attention in the United States.

By 1985 Lihau's health had deteriorated and he was attempting to seek political asylum abroad.
His application to Belgian authorities was refused.
Harvard University invited him to become a visiting scholar at its campus in the United States.
David Heaps, chairman of the board of Human Rights Internet, convinced Mobutu to let Lihau leave the country.
He was subsequently granted political asylum in the United States, and moved to Cambridge, Massachusetts, to become a professor of constitutional law at Harvard.
Meanwhile, in the Congo Mobutu persecuted the UDPS leadership, making it nearly impossible for Party President Étienne Tshisekedi to participate in political activities.
In early 1988 a dozen party executives traveled to Boston and convinced Lihau to assume the presidency of the UDPS.
The following year Lihau founded a political conference with the goal of democratising the Congo.

In April 1990 Mobutu announced he would accommodate multi-party politics.
Lihau, who was at the time presiding over a meeting of exiled politicians in Brussels, demanded that before opposition elements returned to the country Mobutu's government guarantee the tolerance of a genuine multi-party system, agree to organise a round table conference for political reconciliation, and begin disbanding state security forces.
On 22 May he visited the United States Department of State in Washington D.C.. Lihau returned to the Congo and became one of four directors of the UDPS under a reformed leadership model.
The UDPS then entered a coalition with other opposition groups to form the Union Sacrée de l'Opposition, and he served on the union's ruling council.
He joined the UDPS in endorsing the formation of a "Conference Nationale Souveraine" to discuss political reform in the country.
One soon convened, but Lihau protested the large number of delegates summoned by Mobutu to participate, accusing him of trying to stack the representation in his own favor.
Throughout the conference's existence Lihau chaired its constitutional commission.
At one point during the conference, he denounced the perceived Baluba dominance of the UDPS and joined the Alliance des Bangala (ALIBA), a party with financial support from Mobutu that promoted politicians from Équateur.
Eventually the constitutional commission produced a draft recommendation of a federal system that was intended to maintain the national integrity of the Congo while respecting its diversity.
The conference disbanded in December 1992 having greatly reinvigorated democratic thought in the country but ultimately failing to enact significant institutional change.
Lihau went back to the United States to receive medical treatment.

In June 1993 Lihau delivered a speech on television and radio, denouncing the Kasaian ethnic dominance of the UDPS and Tshisekedi's leadership.
The UDPS then labeled him a "traitor" for his association with ALIBA and announce
In 1980, 13 members of Parliament published a letter criticising Mobutu's regime and were arrested for "aggravated treason". Lihau testified on their behalf during the ensuing trial. Two years later he joined them in founding the Union pour la Démocratie et le Progrès Social (UDPS) as an opposition party to Mobutu; Lihau soon became the new party's president. Mobutu was particularly disturbed by Lihau's membership in the party since, as a native of Équateur Province, he added to the geographic diversity of the organisation and therefore its political clout. In retaliation, Mobutu incarcerated him, suspended his rights, confiscated his personal property, and eventually banished him to the village of Yamake in Équateur Province. In August 1983 Lihau joined several of his colleagues in attempting to interrupt a meeting between government officials and United States Congressmen at the Hotel InterContinental in Kinshasa while wearing Western suits and ties (then banned by Mobutu). A violent struggle between the UDPS members and Mobutu's security police ensued in full view of the American delegation and received a great amount of media attention in the United States.
By 1985 Lihau's health had deteriorated and he was attempting to seek political asylum abroad. His application to Belgian authorities was refused. Harvard University invited him to become a visiting scholar at its campus in the United States. David Heaps, chairman of the board of Human Rights Internet, convinced Mobutu to let Lihau leave the country. He was subsequently granted political asylum in the United States, and moved to Cambridge, Massachusetts, to become a professor of constitutional law at Harvard. Meanwhile, in the Congo Mobutu persecuted the UDPS leadership, making it nearly impossible for Party President Étienne Tshisekedi to participate in political activities. In early 1988 a dozen party executives traveled to Boston and convinced Lihau to assume the presidency of the UDPS. The following year Lihau founded a political conference with the goal of democratising the Congo.
In April 1990 Mobutu announced he would accommodate multi-party politics. Lihau, who was at the time presiding over a meeting of exiled politicians in Brussels, demanded that before opposition elements returned to the country Mobutu's government guarantee the tolerance of a genuine multi-party system, agree to organise a round table conference for political reconciliation, and begin disbanding state security forces. On 22 May he visited the United States Department of State in Washington D.C.. Lihau returned to the Congo and became one of four directors of the UDPS under a reformed leadership model. The UDPS then entered a coalition with other opposition groups to form the Union Sacrée de l'Opposition, and he served on the union's ruling council. He joined the UDPS in endorsing the formation of a "Conference Nationale Souveraine" to discuss political reform in the country. One soon convened, but Lihau protested the large number of delegates summoned by Mobutu to participate, accusing him of trying to stack the representation in his own favor. Throughout the conference's existence Lihau chaired its constitutional commission. At one point during the conference, he denounced the perceived Baluba dominance of the UDPS and joined the Alliance des Bangala (ALIBA), a party with financial support from Mobutu that promoted politicians from Équateur. Eventually the constitutional commission produced a draft recommendation of a federal system that was intended to maintain the national integrity of the Congo while respecting its diversity. The conference disbanded in December 1992 having greatly reinvigorated democratic thought in the country but ultimately failing to enact significant institutional change. Lihau went back to the United States to receive medical treatment.
In June 1993 Lihau delivered a speech on television and radio, denouncing the Kasaian ethnic dominance of the UDPS and Tshisekedi's leadership. The UDPS then labeled him a "traitor" for his association with ALIBA and announce
Marcel Lihau