Khomeini was not allowed to return to Iran during the Shah's reign (as he had been in exile). On 16 January 1979, the Shah left the country for medical treatment (ostensibly "on vacation"), never to return. Two weeks later, on Thursday, 1 February 1979, Khomeini returned in triumph to Iran, welcomed by a joyous crowd estimated (by the BBC) to be of up to five million people. On his chartered Air France flight back to Tehran, he was accompanied by 120 journalists, including three women. One of the journalists, Peter Jennings, asked: "Ayatollah, would you be so kind as to tell us how you feel about being back in Iran?" Khomeini answered via his aide Sadegh Ghotbzadeh: "Hichi" (Nothing). This statement—much discussed at the time and since—was considered by some reflective of his mystical beliefs and non-attachment to ego. Others considered it a warning to Iranians who hoped he would be a "mainstream nationalist leader" that they were in for disappointment.
In November 1979, the new constitution of the Islamic Republic was adopted by national referendum. Khomeini himself became instituted as the Supreme Leader (Guardian Jurist), and officially became known as the "Leader of the Revolution." On 4 February 1980, Abolhassan Banisadr was elected as the first president of Iran. Critics complain that Khomeini had gone back on his word to advise, rather than rule the country.
On 22 October 1979, the United States admitted the exiled and ailing Shah into the country for cancer treatment. In Iran, there was an immediate outcry, with both Khomeini and leftist groups demanding the Shah's return to Iran for trial and execution.
In a speech on 1 February 1979 delivered to a huge crowd after returning to Iran from exile, Khomeini made a variety of promises to Iranians for his coming Islamic regime: a popularly elected government that would represent the people of Iran and with which the clergy would not interfere. He promised that "no one should remain homeless in this country," and that Iranians would have free telephone, heating, electricity, bus services and free oil at their doorstep.
Under Khomeini's rule, Sharia (Islamic law) was introduced, with the Islamic dress code enforced for both men and women by Islamic Revolutionary Guards and other Islamic groups. Women were required to cover their hair, and men were not allowed to wear shorts. Alcoholic drinks, most Western movies, and the practice of men and women swimming or sunbathing together were banned. The Iranian educational curriculum was Islamized at all levels with the Islamic Cultural Revolution; the "Committee for Islamization of Universities" carried this out thoroughly. The broadcasting of any music other than martial or religious on Iranian radio and television was banned by Khomeini in July 1979. The ban lasted 10 years (approximately the rest of his life).
Shortly after his accession as supreme leader in February 1979, Khomeini imposed capital punishment on homosexuals. Between February and March, sixteen Iranians were executed due to offenses related to sexual violations. Khomeini also created the "Revolutionary Tribunals". According to historian Ervand Abrahamian, Khomeini encouraged the clerical courts to continue implementing their version of the Shari’a. As part of the campaign to "cleanse" the society, these courts executed over 100 drug addicts, prostitutes, homosexuals, rapists, and adulterers on the charge of "sowing corruption on earth." According to author Arno Schmitt, "Khomeini asserted that 'homosexuals' had to be exterminated because they were parasites and corruptors of the nation by spreading the 'stain of wickedness.'" Transsexuality was designated by Khomeini as a sickness that was able to be cured through surgery. In 1979, he had declared that the execution of homosexuals (as well as prostitutes and adulterers) was reasonable in a moral civilization in the same sense as cutting off decayed skin.
In a talk at the Fayzieah School in Qom on 30 August 1979, Khomeini warned pro-imperialist opponents: "Those who are trying to bring corruption and destruction to our country in the name of democracy will be oppressed. They are worse than Bani-Ghorizeh Jews, and they must be hanged. We will oppress them by God's order and God's call to prayer."
Zoroastrians, Jews, and Christians are officially recognized and protected by the government. Shortly after Khomeini's return from exile in 1979, he issued a fatwa ordering that Jews and other minorities (except those of the Baháʼí Faith) be treated well. In power, Khomeini distinguished between Zionism as a secular political party that employs Jewish symbols and ideals and Judaism as the religion of Moses.
One non-Muslim group treated differently were the 300,000 members of the Baháʼí Faith. Starting in late 1979 the new government systematically targeted the leadership of the Baháʼí community by focusing on the Baháʼí National Spiritual Assembly (NSA) and Local Spiritual Assemblies (LSAs); prominent members of NSAs and LSAs were often detained and even executed. "Some 200 of whom have been executed and the rest forced to convert or subjected to the most horrendous disabilities."
After the Shah left Iran in 1979, a Kurdish delegation traveled to Qom to present the Kurds' demands to Khomeini. Their demands included language rights and the provision for a degree of political autonomy. Khomeini responded that such demands were unacceptable since it involved the division of the Iranian nation. The following months saw numerous clashes between Kurdish militia groups and the Revolutionary Guards. The referendum on the Islamic Republic was massively boycotted in Kurdistan, where it was thought 85 to 90% of voters abstained. Khomeini ordered additional attacks later on in the year, and by September most of Iranian Kurdistan was under direct martial law.