Tourism is an increasingly popular economic development strategy in many countries. Although the revenue earned through tourism industry can be more than the oil and natural resources revenue in some countries, many economic activities which are allowed by non-religious economic schools are prohibited in Islam due to their individual and social negative impacts and the evil which they entail. These illicit activities are in fact the restricted areas which a Muslim is forbidden to enter. Naturally, the revenues from such activities, in addition to its prescriptive prohibition, leave adverse effects on the individual and social ethics of society. Considering that prohibited incomes or revenues are not at the same degree of filthiness, their effects on morality will also be varied but there is no doubt that all of them have a role to play in wiping off moral virtues and human excellences. The adverse effects of these incomes on individual morality are the following: Blackness of the heart, perversion, baseness, depravity, lineal degradation, spiritual risks etc.
Also, the adverse effects of these incomes on the social morality are: dominance of promiscuity, elimination of public virtues and eventually destruction of society. That is because of the fact that if divine limits are not observed in society, the social morality and human values will be eradicated and chaos will permeate the society.
It is pertinent to mention that non-Muslims are not persecuted, if some of the Islamic prohibitions such as drinking wine, eating pork etc. are committed by them clandestinely.
Tourism is an industry and an important source of revenue for some countries. However, there are certain barriers in Shari'ah for its promotion in an absolute manner. These barriers shall be studied below in two separate parts: material and spiritual.
First part: The Material Barriers
One of the issues being the focus of attention is the subject of earnings which should be lawful. The revenues earned through prohibited ways, in addition to its prescriptive prohibition, leave adverse effects on the individual and social morality of society. Some of those effects are: Blackness of the heart, perversion, baseness, depravity, lineal degradation etc.
Some of the examples of prohibited earnings which are relevant to the subject of the question are: the money which an adulterer or prostitute receives, the income from producing intoxicating drinks which includes all stages, forms and procedures, the money from gambling etc.
In fact, it is necessary to note that although these prohibitions are particular to Muslims, if non-Muslims are allowed to practice these prohibitions freely, then they (prohibitions) will spread throughout the society because the spread of such things conventionally means that the Islamic government has allowed and legalized them.
Second part: Spiritual Barriers
The spiritual barriers include several things which will be studied under the following categories:
A) Promotion of Falsehood
One of the negative effects and consequences of the travels made by non-Muslim tourists to a Muslim country can be deviation of the society from the Islamic course. Some tourists do not aim to visit an Islamic country only but they also endeavor to spread their culture and beliefs. The Holy Quran says: "And the Jews will not be pleased with you, nor the Christians until you follow their religion. Say: Surely Allah's guidance, that is the (true) guidance. And if you follow their desires after the knowledge that has come to you, you shall have no guardian from Allah, nor any helper." The message that this verse conveys is that the enemy is not pleased with little; they will be pleased only with utter destruction and elimination of the school and of your goals and ideals.
B) Dual Approaches in Muslim Community
The religion of Islam attaches great importance to respecting women's chastity and their honor. For this reason, it has enacted rules and limits such as "modest dressing" for women and forbidden men from gazing at women and behaving promiscuously. Islam has set "privacy" for women which the strangers are not allowed to violate. Keeping this point in mind, it is not possible to ask Muslims to adhere to such rules and in the meantime let non-Muslims free to promote and spread their own liberal promiscuous culture in Islamic countries.
C) Freedom of the Followers of other Religions in Islamic Countries with Respect for Our Religious Principles
It is also the duty of Islamic government to fight all polytheistic symbols as well as forms of idolatry in the same way as the great Prophet of Islam, peace be upon him and his family, destroyed the idol houses and broke the idols. For this reason, the dhimmis or the non-Muslim populations living in Islamic countries under the protection of Islamic government do not have the right to openly violate Islamic religious rules and commit such acts that are forbidden under Shari'ah law. For instance, they cannot eat and drink openly in the holy month of Ramadhan nor can they drink alcoholic beverages or eat pork and the likes. It is not permissible for them to ring the church bell without permission from the Islamic government. In case, however, they commit such offensive acts in their own specific premises such as churches or special stores for them, none will object to them.
In conclusion, it should be said that in view of the fact that the Iranian law is derived from Islamic jurisprudence, it is not possible to include rules in it rules that are against the jurisprudence.
See question 8167 (site: 8303) in this regard.
 - Shaykh Ansari (r.a.) has named various kinds of haram earnings and professions in the commentary of a narration cited from Tohaful Uqul. See: Ansari, Murteza, Al-Makasib al-Muharramah, vol.1, pg. 13, Dar al-Zakhaer Publications, qom, 1411 A.H.
 - Al-Baqarah, 120
 - Al-Ahzab, 59
 - Al-Noor, 30