TUCSON, Ariz. — A federal judge in Tucson has dropped the final charge against a humanitarian volunteer who was arrested while trying to help migrants in the Arizona desert.

Scott Warren was scheduled to be sentenced Thursday for a misdemeanor conviction of driving in a wilderness area. 

Prosecutors asked U.S. District Judge Raner C. Collins to dismiss the case with prejudice, meaning the charge cannot be brought again. 

They didn’t immediately say why they asked for the case to be dismissed.

 Warren, 37, was acquitted in November of felony charges of harboring two Central American migrants who spent several days at an aid station in Ajo.

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Scott Warren, center, of Ajo, Ariz., celebrates with his attorneys Amy Knight, right, and Greg Kuykendall outside court in Tucson, Ariz. on Wednesday, Nov. 20, 2019, after being acquitted of two counts of harboring in a case that garnered international attention. Prosecutors said Warren illegally helped two migrants avoid authorities. He said he was fulfilling his humanitarian duties by helping two injured men. (AP Photo/Astrid Galvan)
AP