SAN FRANCISCO — Rolland Gregg and his family have fought federal marijuana charges for more than three years, arguing that the roughly 70 marijuana plants investigators found on their Washington property were for their own medicinal use and fully complied with state law.A federal jury last year convicted Gregg, his mother and his then-wife of growing 50 to 100 marijuana plants — amounts their attorney said are in compliance with state medical marijuana law.With prison sentences looming, they have now turned to …