Why was this case tried by a court-martial?

Off-base sexual assault against a civilian. Why did the Coast Guard try this case rather than civilian authorities? (And no, the presence of false statements about the offense to military investigators doesn't answer the question.)

How's this for an example of uncritical reporting?

"The case was handled in military court because of the alleged violation of Article 120 of the Uniform Code of Military Justice, [spokesperson Lt. Dana] Warr said. Article 120 deals with rape and sexual assault."

Did the local civilian prosecutor refuse to prosecute? The article doesn't say.