The Ol' Duff is back to making his old expense claims.

Shortly after his court vindication, Senator Mike Duffy returned to charging taxpayers for some of his Ottawa living expenses.

According to the Senate's quarterly proactive disclosure report, Duffy claimed $1,691.59 in National Capital Region expenses between March and June of 2016.

These are the types of claims that led to the Senate expenses scandal in the first place, and prompted an overhaul of the rules and regulations for the Upper Chamber.

"I filed my claims as the Senate rules provide, and was approved by Senate administration, and as Judge Vaillancourt agreed were valid," Duffy told CBC News in an email.

Before the scandal broke in 2013, it had been widely known that Duffy, who represents Prince Edward Island, had lived in Ottawa for more than two decades during his time as a television broadcaster.

Duffy's previous expense claims led to a criminal investigation, and he was charged with 31 counts of fraud and breach of trust. After a year-long legal saga, Duffy was found not guilty on all charges in a resounding victory issued by Justice Charles Vaillancourt.

Duffy within the rules

While Duffy's previous claims landed him in court, there appears to be no uncertainty about whether he is entitled to make Ottawa living expense claims now.

Senate administration confirms Duffy is well within the rules, as he has proved he is a resident of Prince Edward Island.

In an email to CBC News, Senate spokeswoman Jacqui Delaney says "as per the new rule adopted in May 2013, Senator Duffy has submitted a Declaration of Provincial/Territorial Residence and National Capital Accommodation with the following supporting documents:

Senator's driver's licence.

Senator's provincial health card.

Notice of assessment from the Canada Revenue Agency.

"This declaration and supporting documents must be submitted annually," Delaney added.

More Senate reform needed: CTF

After learning of Duffy's new Ottawa expense claims, the Canadian Taxpayers Federation is questioning whether the Senate's new rules on expenses go far enough.

"After Mr Duffy was acquitted, there was a lot of concern about the rules and whether the rules were tight enough," said Aaron Wudrick, federal director of the CTF.

"We were assured by the Senate that the rules had been tightened, and that they had been changed. But if he's still able to claim, that suggests that the rules haven't been tightened enough," Wudrick added.

"It's the same issue with his trial. He was technically within the rules, but that just casts aspersions on the rules. It suggests the rules mean nothing if you can actually live within them and still get away with this," Wudrick said.

Mike Duffy's residency - whether he lives in Ottawa or P.E.I., the province he represents in the Senate - was at the centre of his long-running fraud and breach of trust trial. In the end, the judge saw it his way, finding the Senate rules unclear. (Sean Kilpatrick/The Canadian Press)

But some of Duffy's colleagues are more supportive of his claims.

"He is able to claim expenses in accordance with Senate rules like any other senator," said Senator Peter Harder, one of the Upper Chamber's newest members.

"As you know, these [rules] have been significantly clarified and made for more transparency in the past two years," Harder added.

The Prime Minister's Office wouldn't comment specifically on Duffy's new expense claims.

"We remain confident in the prime minister's new approach to make the Senate less partisan and more independent," PMO spokesman Cameron Ahmad said in an email to CBC News.