Wa `alaykum As-Salamu waRahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear questioner, we would like to thank you for the great confidence you place in us, and we implore Allah Almighty to help us serve His cause and render our work for His Sake.
Answering your question, Dr. Mohammad S. Alrahawan, Associate Professor at the department of Islamic Studies in English, Al-Azhar University, Egypt, states:
A muhrim is the one who commenced on the state of ihram. Ihram is the sacred state in which a Muslim carries out the required rituals to complete Hajj or `Umrah.
However, a muhrim also has to wear special clothing that is designed for the purpose of performing `Umrah or Hajj. Once a person enters into the state of ihram, he/she is prohibited to do certain practices. He/she should not conduct a marriage contract, have sexual intercourse, or make a marriage proposal. This is based on the hadith narrated by `Uthman (may Allah be pleased with him) that the Prophet (peace be upon him) said: “A muhrim (a pilgrim in the state of Ihram) should not marry, or give in marriage, or betroth.” (Muslim)
Once he/she finishes ihram by shaving or having hair cut, he or she can do whatever was prohibited during their ihram whether they still live in Makkah or not.
It is not permissible to make a proposal of marriage when a person is in the state of ihram whether a person is in Makkah or outside Makkah. He can make it after terminating `Umrah even in Makka or at the Sacred Mosque of Makkah. Therefore, if the contract had been concluded while the bride and/or groom are/is still muhrim, such a contract would not have been valid. They must make the contract again, since it is not effective. If both of them do not know the legal ruling, they do not incur a sin but the contract is still invalid.
Allah Almighty knows best.