What is the ruling on working with humanitarian aid organizations such as the Red Cross, Red Crescent, and others? And what is the ruling on non-Syrians working with these organizations in Syria?

Relief work is desirable and sometimes obligatory. It contains a lot of good and falls under the multiple categories of charity, as mentioned in the noble Hadith. It is permissible to work with Islamic relief organizations such as the Red Crescent, as long as there is no Shariah prohibition. As for the Red Cross, the default is that it is not permissible to work with them unless no other option is available and work can only be facilitated through them.