Rubin was in court Thursday with Arnao, who was convicted of a variety of corruption charges on Monday along with former state Sen. Vincent Fumo.
The hearing was about prosecutors seeking millions of dollars in forfeiture from Fumo following his conviction on all 137 fraud and obstruction counts.
It was there Rubin was handed a "target letter" from the FBI, letting him know he was the target of an investigation.
"As everyone in the courtroom saw, one of the FBI agents did hand him an envelope in which there was a letter, but I'm not going to make any comment on the contents at this point," Jacobs said.
The original indictment against Fumo describes Rubin as a no-work Senate employee hired by Fumo as an outside contractor, before he was named chairman of the Turnpike Commission.
The indictment also named Michael Palermo, a friend of Fumo's who was paid $220,000 as a consultant for the Turnpike Commission.
The government alleges that Palermo didn't do any work for the Commission, instead spent his time managing Fumo's 100 acre farm outside Harrisburg.
In his closing argument during the Fumo trial, prosecutor Bob Zausmer referred to Rubin and Palermo as co-conspirators.
The government would not say whether or not Palermo is also a target.
The Feds now appear to be casting a wider web as the investigation continues, on the verge of snaring more of Fumo's loyal friends.
Rubin has been under pressure to resign.
Senate Majority Leader Dominic Pileggi says Rubin should explain himself. He says if Rubin can't give an adequate explanation, he should resign immediately and return the money from the consulting job to the state.
Fumo will be sentenced on July 13th. He could get up to 20 years in prison for defrauding the senate, a nonprofit and a museum.
The Associated Press contributed to this report.
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