Ayaz Mutalibov, who briefly served as president after the former Soviet nation gained independence in 1991, is benefiting from recently approved legislation granting all heads of state immunity from prosecution for acts committed while in office.
He was accused by prosecutors of involvement in the bloody Soviet crackdown on pro-independence demonstrators in 1990 and later of attempting to overthrow the post-independence government.
The Social-Democratic Party said Monday that its co-founder flew into the country over the weekend.
Mutalibov announced earlier this year that he would abstain from political activity.
The law approved by parliament in June extends immunity to incumbent President Ilham Aliyev and his wife.