Is the marriage of a Sunni woman to a non-Sunni man permissible or forbidden?

The ruling on marrying an innovator (mubtadi‘) varies depending on the nature of the innovation. If the innovation is one that leads to disbelief (kufr)—such as slandering the Companions or claiming that the Qur’an has been distorted—then it is not permissible to marry him, based on Allah’s saying: {And do not marry [your women] to polytheists until they believe.} [Q. 2:221]. However, if the innovation does not lead to disbelief—such as celebrating the Prophet’s birthday (Mawlid)—then it is permissible to marry him. Nevertheless, it is better for her not to marry anyone unless she is pleased with his religion and character, in accordance with the hadith: “If someone whose religion and character you are pleased with comes to you seeking marriage, then marry him.”