Etheridge and Rundgren were arrested in August and September, respectively, but the details on the arrests have just surfaced, via TMZ.
Both incidents occurred when the rockers were crossing the U.S. border into North Dakota.
The U.S. Customs and Border Patrol searched Etheridge's tour bus on Aug. 17 using a drug sniffing K-9 unit. The animals discovered marijuana oil, which the "Come to My Window" singer claimed was used medicinally to fight pain from breast cancer.
The oil is legal in California, where she resides, but is illegal in North Dakota. She was booked on possession of a controlled substance but plead not guilty to the charge.
Rundgren's bust occurred on Sept. 9. A K-9 unit didn't find any drugs on his bus, but Border Patrol agents discovered two vapes and containers with liquid THC.
The "I Saw the Light" singer was booked on a possession of drugs and paraphernalia charge. No word on how he's pleading his case.
Neither musician has spoken out about their respective charges as of yet.