Honor Killings have been a big issue in the Islamic countries from Arabic countries to Indonesia. In fact some Muslim women living in US and UK have been victims of this practice – where the family thinks that it is important to uphold the family honor – over and above the life of a person. Here is a definition:
An honor killing or honour killing is the murder of a family or clan member by one or more fellow family members, when the murderers (and potentially the wider community) believe the victim to have brought dishonour upon the family, clan, or community, normally by (a) utilising dress codes unacceptable to certain Islamic people or (b) engaging in certain sexual acts. These killings result from the perception that defense of honour justifies killing a person whose behavior dishonours their clan or family.
Look at the stories of these women:
Hatin Surucu just wanted to live her own life. Instead, she became Berlin’s latest victim of honor killings. Her Turkish Muslim brothers allegedly gunned her down for adopting Western ways.
Twenty-year-old Banaz Mahmod was strangled in a so-called “honour” killing and buried in a suitcase in a back garden. Her father and uncle have been convicted of her murder. Sky’s Orla Chennaoui reports.
The 16-year-old Mississauga girl was strangled by her father in a dispute over her refusal to wear the hijab as an honor killing. 
Honor Killing: not a crime – Pak High Court
Now, Pakistan’s Lahore High Court has said that Honor Killings are not a crime. The judge was Justice Asif Saeed Khosa.
The court acquitted Ghulam Nabi and his son Iftikhar, saying murder to save a woman’s honour was not a crime. The accused had killed one Yasin while saving a female relative’s honour. The trial court sentenced them to 10 years’ imprisonment but the LHC acquitted them.
Some critics of Honor killings cite this verse from the Hadith book 017 as one of the evidence in Islamic scriptures that encourage the honor killings.
Sahi Muslim No. 4206 (Book 017): 
‘Abdullah b. Buraida reported on the authority of his father that Ma’iz b. Malik al-Aslami came to Allah’s Messenger (may peace be upon him) and said: Allah’s Messenger, I have wronged myself; I have committed adultery and I earnestly desire that you should purify me. He turned him away. On the following day, he (Ma’iz) again came to him and said: Allah’s Messenger, I have committed adultery. Allah’s Messenger (may peace be upon him) turned him away for the second time, and sent him to his people saying: Do you know if there is anything wrong with his mind. They denied of any such thing in him and said: We do not know him but as a wise good man among us, so far as we can judge. He (Ma’iz) came for the third time, and he (the Holy Prophet) sent him as he had done before. He asked about him and they informed him that there was nothing wrong with him or with his mind. When it was the fourth time, a ditch was dug for him and he (the Holy Prophet) pronounced judg- ment about him and he wis stoned. He (the narrator) said: There came to him (the Holy Prophet) a woman from Ghamid and said: Allah’s Messenger, I have committed adultery, so purify me. He (the Holy Prophet) turned her away. On the following day she said: Allah’s Messenger, Why do you turn me away? Perhaps, you turn me away as you turned away Ma’iz. By Allah, I have become pregnant. He said: Well, if you insist upon it, then go away until you give birth to (the child). When she was delivered she came with the child (wrapped) in a rag and said: Here is the child whom I have given birth to. He said: Go away and suckle him until you wean him. When she had weaned him, she came to him (the Holy Prophet) with the child who was holding a piece of bread in his hand. She said: Allah’s Apostle, here is he as I have weaned him and he eats food. He (the Holy Prophet) entrusted the child to one of the Muslims and then pronounced punishment. And she was put in a ditch up to her chest and he commanded people and they stoned her. Khalid b Walid came forward with a stone which he flung at her head and there spurted blood on the face of Khalid and so he abused her. Allah’s Apostle (may peace be upon him) heard his (Khalid’s) curse that he had huried upon her. Thereupon he (the Holy Prophet) said: Khalid, be gentle. By Him in Whose Hand is my life, she has made such a repentance that even if a wrongful tax-collector were to repent, he would have been forgiven. Then giving command regarding her, he prayed over her and she was buried.
1. Wikipedia: Honor Killings
2. The Whore Lived Like a German
3. Girl, 16, dies after hijab dispute with father
4. Murder while saving woman’s honour not a crime: LHC
5. Sahih Bukhari’s Hadith Collection (No. 4206)