What would the constitution of an Islamic caliphate look like today?

This is the first few sections providing an overview of the Draft Constitution of contemporary Khilafah State published by the Islamic political party Hizb ut-Tahrir in 2010. You can find the full copy of it here:

GENERAL RULES Article 1 The Islamic 'Aqeedah constitutes the foundation of the State. Nothing is permitted to exist in the government's structure, accountability, or any other aspect connected with the government, that does not take the 'Aqeedah as its source. The 'Aqeedah is also the source for the State's constitution and shar'i canons. Nothing connected to the constitution or canons is permitted to exist unless it emanates from the Islamic 'Aqeedah. Article 2 The domain of Islam (Daar ul-Islam) is that entity which applies the rules of Islam in life's affairs and whose security is maintained by Muslims. The domain of disbelief (Daar ul-Kufr) is that entity which applies the rules of kufr and whose security is maintained by the kuffaar. Article 3 The Khaleefah is empowered to adopt divine rules (aHkaam shar'iyyah) enacted as constitution and canons. Once the Khaleefah has adopted a divine rule, that rule alone becomes the divine rule that must be enacted and then implemented. Every citizen must openly and secretly obey that adopted rule. Article 4 The Khaleefah does not adopt divine rules pertaining to worship, i.e. ibadaat, except in connection with alms (zakaah) and war (jihaad) in addition to that which is necessary for maintaining the unity of muslims. Also, he does not adopt any of the thoughts connected with the Islamic 'Aqeedah. Article 5 All citizens of the Islamic State are entitled to enjoy the divine rights and they are bound by the divine duties. Article 6 All citizens of the State shall be treated equally regardless of religion, race, colour or any other matter. The State is forbidden to discriminate among its citizens in all matters, be it ruling or judicial, or caring of affairs. Article 7 The State implements the aHkaam shar'iyyah on all citizens who hold citizenship of the Islamic State, whether Muslims or not, in the following manner: a. The aHkaam shar'iyyah is implemented in its entirety, without exception, on all Muslims. b. Non-Muslims are allowed to follow their own beliefs and worships. c. Those who are guilty of apostasy (murtadd) from Islam are to be executed according to the rule of apostasy, provided they have by themselves renounced Islam. If they are born as non-Muslims, i.e., if they are the sons of apostates, then they are treated as non-Muslims according to their status as being either polytheists (mushriks) or People of the Book. d. In matters of food and clothing the non-Muslims are treated according to their religions within the limits allowed by ahkam Shara'iah. e. Marital affairs (including divorce) among non-Muslims are settled in accordance with their religions, but between non-Muslims and Muslims they are settled according to the aHkaam shar'iyyah. f. All the remaining shar'i matters and rules, such as: the application of transactions, punishments and evidences (at court), the system of ruling and economics are implemented by the State upon everyone, Muslim and non-Muslim alike. This includes the people of treaties (mu'aahid), the protected subjects (ahlu ZHimmah) and all who submit to the authority of Islam. The implementation on these people is the same as the implementation on the subjects of the State. Ambassadors and envoys enjoy diplomatic immunity. Article 8 Arabic is the language of Islam and the sole language of the State. Article 9 Ijtihaad (exertion to derive the Islamic rule) is fard kifaayah (a collective duty). Every Muslim has the right to exercise ijtihaad if he has acquired the necessary conditions to perform it. Article 10 There is no such thing as a clergy in Islam as all Muslims bear the responsibility for Islam. The State will prevent anything that indicates the existence of a clergy among Muslims. Article 11 The primary function of the State is the propagation of the call (da'wah) to Islam. Article 12 The only evidences to be considered for the divine rules (aHkaam shar'iyyah) are: the Qur'an, the Sunnah, the consensus of the Companions (ijmaa' as-SaHaabah) and analogy (qiyaas). Legislation cannot be taken from any source other than these evidences. Article 13 Every individual is innocent until proven guilty. No person shall be punished without a court sentence. Torturing is absolutely forbidden and whoever inflicts torture on anyone shall be punished. Article 14 All human actions are, in origin, restricted by the divine rules (aHkaam shar'iyyah) and no action shall be undertaken until its rule (Hukm) is known. Every thing or object is permitted, i.e., Halaal, unless there is an evidence of prohibition. Article 15 Any means that most likely leads to a prohibition (Haraam) is itself Haraam. However if it was (only) feared that it may lead to a prohibition, then it would not be Haraam. THE RULING SYSTEM Article 16 The ruling system of the State is that of a unitary ruling system and not a federation. Article 17 Ruling is centralised and administration is de-centralised. Article 18 There are four positions of ruling in the State. They are: The Khaleefah , the delegated assistant (mu'aawin at-tafweeD), the governor (wali) and the provincial mayor (a'mil). All other officials of the State are employees and not rulers. Article 19 No one is permitted to take charge of ruling, or any action considered to be of the nature of ruling, except a male who is free (Hurr), i.e. not a slave, mature (baaligh), sane ('aaqil), trustworthy ('adl), competent; and he must not be save a muslim. Article 20 Calling upon the rulers to account for their actions is both a right for the Muslims and a farD kifaayah (collective duty) upon them. Non-Muslim subjects have the right to make known their grievances regarding the rulers injustice and misapplication of the Islamic rules upon them. Article 21 Muslims are entitled to establish political parties to question the rulers and to access the positions of ruling through the Ummah on condition that the parties are based on the 'Aqeedah of Islam and their adopted rules are aHkaam shar'iyyah; the establishment of such a party does not require a license by the State. Any party not established on the basis of Islam is prohibited. Article 22 The ruling system is founded upon four principles. They are: 1. Sovereignty belongs to the divine law (shara') and not to the people. 2. Authority belongs to the people, i.e., the Ummah. 3. The appointment of one Khaleefah into office is an obligation upon all Muslims. 4. Only the Khaleefah has the right to adopt the aHkaam shar'iyyah and thus he passes the constitution and the various canons. Article 23 The State systems are made up of thirteen institutions. They are: 1. The Khaleefah (Al-khaleefah). 2. The delegated assistant (mu'aawin at-tafweed). 3. The executing assistants (mu'aawin at-tanfeeZH). 4. Governors (Wulaah). 5. Amir of jihad (Ameerul jihad). 6. Home land (Interior) security. 7. Foreign affairs. 8. Industry. 9. Judiciary (QuDaa'a). 10. The state departments (maSaaliH ad-dawlah). 11. State treasury (Bayt ul-mal). 12. Media (I'laam). 13. The council of the Ummah (Shura and accounting). THE KHALEEFAH Article 24 The Khaleefah is represents the Ummah in authority and in implementing the shara'. Article 25 Khilafah is a contract of nomination and acceptance. No one is obliged to accept it and no one is obliged to nominate a particular person for it. Article 26 Every mature male and female Muslim, who is sane, has the right to participate in the election of the Khaleefah and in giving him the pledge (ba'iah). Non-Muslims have no right in this regard. Article 27 Once the contract of the Khilafah has been concluded on a person through the ba'iah of those by whom the ba'iah is legitimately concluded, the ba'iah of the remaining people is a ba'iah of obedience and not contract. Consequently, those who might disobey or rebel are obliged to give ba'iah. Article 28 Nobody can become Khaleefah without being appointed by the Muslims. Nobody can hold the power of the Khilafah unless it is convened to him legitimately, as is the case with any contract in Islam. Article 29 Any country that wishes to give the Khaleefah the ba'iah of contract, her sulTaan (authority) must be self-acting, that depends on Muslims only and not on any kaafir state. The security of the Muslims in that country, both internally and externally, must be maintained by the security of Islam and not kufr. As for the ba'iah of obedience only, it can be taken from any other country without such conditions. Article 30 The individual who is given the ba'iah for Khilafah need only to fulfill the contracting conditions, even if he did not fulfil the preference conditions, because what is essential is the conditions of contracting.