Effective June 30, 2018, the Transportation Security Administration will begin denying powder-like substances that are over 12 oz/350 mL in carry-on luggage on international flights.
Powders & powder-like substances in containers 12 oz/350 mL or larger that cannot be identified by TSA officials at security check points are subject to being confiscated and destroyed.
To avoid this, TSA is suggesting that such be packed in checked luggage.