Green’s Dictionary of Slang

acceptable, correct; on pattern of kosher adj. (1)

2006		G. Malkani Londonstani (2007) 65: Clearly this wasn’t exactly halal on her part an so it made some people call her a ho.
2008		N. Drayson Birds East Africa 120: Is this kosher? I hear you ask. Is it halal? Can this really be viewed as strict adherence to the letter and spirit of the competition?