This has been explained in a Q&A by Sheikh Taqiuddin an-Nabhani on 14th August, 1967, the following is the relevant portion of his answer:
"There is a point which is misunderstood by some Shabab which is the difference in the Yameen (oath) between adoption and executing an order. The Yameen (oath) does not say that I will adopt even if it goes against my opinion. It just says, “adopt.” When the Yameen talked about obeying a command, it said executing the command even if it is against my opinion. If a judgment is issued it has to implemented even if it goes against the persons opinion. This is a natural law in the Universe since the beginning of humanity till the Day of Judgment.
Adoption of the party is different from that of the Khalifah. Adoption by the Khalifah is a command which all Muslims have to obey regardless of their opinion. It is a Fard to obey the Imam whether publicly or privately. His decision has to be implemented even if it goes against the opinion of the one who is implementing it. The adoption of the Khalifah is not to be taken as an adoption rather as a command that people do not have to adopt but implement it. However, when it comes to the adoption of the party then it is an adoption for each and every and every member. The issue is not a command to be implemented rather it is an opinion which represent the party. The Hizb is the entire Shabab and its apparatus. The definition of the Hizb as mentioned is a structure adopting an ideology which its member believe in and are willing to apply it. The structure is a collection of people based on one idea, so whatever the structure adopts it has to be adopted by each and every member. Issue of disagreement should not arise on this matter and is not an issue to begin with. So whatever is adopted will be explained, published, and will represent the opinion of Hizb ut-Tahrir. Everyone has the right to discuss, investigate, research the daleel, implementation of the daleel, and consider it their opinion. Since, it is the opinion of the party. If a person did not comprehend or agree then it is still his opinion and he should leave his personal opinion. The example of a Mujtahid leaving his ijtihad for others ijtihad is common. Even the great Sahabah practiced this. It was well known that Umar left his opinion for Ali’s, Abu Bakr left his opinion for Ali’s, and Uthman left his opinion for Umar’s. There are many example of this. If the individual did not agree, he has to leave his opinion and adopt Hizb’s opinion. After Hizb adopts an opinion it becomes his opinion.
This is the difference between adopting the ideas and performing the decisions. The adopted ideas of the Hizb automatically becomes the adopted ideas of each member in the party. The decisions to perform an order is not an adoption but orders to be carried out and performed. They are not adopted but are implemented even if it goes against the opinion of the one who executes it. This is also another difference between the adoption of the Khalifah and the adoption of the Hizb. The adoption of the Khalifah does not bind the Ummah to adopt the adoption at hand rather it binds the Ummah to implement the adoption. Whereas, the adoption of the Hizb does not necessarily manifest in the implementation of the idea. Rather it as an adoption that stays with a person for his entire life even if it is not implemented. Therefore, it is a major error and ignorance on the part of the member to claim that this is Hizb opinion whereas my opinion is something else. No member should have another opinion other than what the Hizb has adopted because every member is the party and the party is one homogenous entity in its thoughts and emotions. Consequently, even if a member is Mujtahid Mutlaq (Absolute Mujtahid), he must leave his opinion and adopt the ideas of the Hizb immediately. If he refuses to do this then he has to leave the party since his membership is no longer valid even if he did not adopt one single idea. Not completely adopting what the Hizb has adopted means abandoning the concept of adoption. When the Shab joined the Hizb he studied the Aqeedah of the party and was aware and convinced of its culture and ideas. He accepted and committed himself to adhere to it. This could have happened whether through studying the ideas in detail or having a general satisfaction with the Hizb. Therefore, after the Shab joined the Hizb he automatically and naturally adopted whatever the party has adopted and will adopt in the future. The question is not being convinced in each and every single idea, rather it is being convinced in the entire set of ideas and its details. The issue is not of Taqleed, a fellowship, ijtihad, or research requiring investigating in every idea and its daleel. The matter is having one party based on one idea and to be part of this group the person has to adopt the party’s opinion. If he does not then he does not have to join the party.
14th August, 1967."