A year ago, gasoline mogul Eyob “Joe” Mamo had reason to sweat: The District’s attorney general had announced an antitrust probe into his extensive service-station holdings, and a key D.C. Council member had just moved to resurrect legislation that would drastically shake up his business model.

These days, Mamo can breathe easier.

After a bruising battle on which he lobbied heavily, the council rejected the Mamo-targeted bill, sponsored by Mary M. Cheh (D-Ward 3), in a February vote. And on Friday, Attorney General Irvin B. Nathan announced he won’t be bringing suit against Mamo’s Capitol Petroleum Group for unfair trade practices.

Nathan, addressing the probe in an interview with WAMU-FM’s Politics Hour, said the decision not to sue followed a “very intensive investigation” that including hiring outside experts and purchasing gas price data.

Mamo, seen last May. (Mark Gail/WASHINGTON POST)

Long story short, the case was a long shot, and it wasn’t worth it to Nathan to tie up some of his best lawyers for months on a high-risk case.

Nathan did raise the prospect that private parties — likely gasoline customers or station operators — might file class-action lawsuits against Mamo’s Springfield-based company. If that happened, he said, the city might get involved in some manner: “I wouldn’t say that our investigation would be completely over, but at the appropriate time, particularly if there is private litigation that is is brought, we will make known to the court and therefore to the public what we have found about the results.”

Mamo’s representatives could not be immediately reached for comment.

In other comments Friday, Nathan discussed campaign finance reform legislation he expects to submit to the public by month’s end. He also praised his boss, Mayor Vincent C. Gray, and his record as mayor, as Gray faces revelations of an illegal “shadow campaign” and calls for his resignation.

“In my judgment, this is an honest man who is doing a very good job as the mayor,” Nathan said. “He is, in everything I’ve seen, ethical. There’s no cutting of corners. There’s no evasion of the law with respect to anything that’s going on in the governing of the District.”

Gray on Wednesday called on residents to distinguish between the functioning of his administration and the “issues” in his campaign.

Nathan said the ongoing investigation into the latter is “very serious” and “should be continued.”