BOGOTA (Reuters) - Colombia's President Juan Manuel Santos on Wednesday signed a decree to restore Gustavo Petro as mayor of Bogota, just weeks after a judicial authority dismissed him for mismanagement of waste collection.

The president's ruling could be overruled by a higher judiciary body, and some are concerned that this could leave the capital city without steady leadership until elections in two years.

Bogota has already had two stand-in mayors since Petro left on March 19. Late on Tuesday, a Bogota tribunal ruled that Santos must adhere to the Inter-American Human Rights Commission request that the leftist Petro be reinstated.

Petro, 54, had been a member of the now-defunct M-19 guerrilla movement which disbanded to embrace politics. He left office when Santos ratified a decision by the Council of State, the senior judicial authority that dismissed him.

"I have said from the first day that this process began that for me the norms of conduct, my guide, have been simple and clear: abide by the constitution," Santos said during an address in the presidential palace.

"So in this case, the law has said I must reinstate Mayor Petro, so I have signed the corresponding decree."

In a Tweet last night, Petro said the Bogota court protected his human rights.

Petro's dismissal was declared in December by right-wing Inspector General Alejandro Ordonez over the mayor's attempt to reclaim management of waste collection from private operators.

Poor planning resulted in garbage piling up in the streets before the duties were returned to private contractors.

The inspector general's office probes mismanagement by public officials.

Petro's ouster caused nationwide controversy. Many were especially critical of a decision by Ordonez to also ban Petro from holding public office for 15 years. Critics called this a move by the traditionally right-leaning political establishment to undermine leftist opponents.

Many observers view Petro's difficulties as a right-wing campaign against the left and future political participation by Marxist FARC rebels if ongoing peace talks are successful.

The FARC, or Revolutionary Armed Forces of Colombia, is negotiating a five-point peace accord with the government to end a half-century of conflict that has killed more than 200,000 people.

(Reporting by Helen Murphy and Monica Garcia)