When Ames was arrested espionage was no longer a capital offence. After his arrest, Congress passed legislation making certain acts of espionage a capital offence.
Hanssen’s wife didn’t receive his full pension. According to David Vise’s “The Bureau and the Mole,” she received exactly the same pension as if he had died.
The purpose of the pension is to provide the intel community with continuing leverage to ensure Hanssen’s cooperation. Debriefing of a mole can take years, if he stops cooperating, the FBI can shut off his wife’s pension. It was part of the deal prosecutors worked out to determine what Hanssen revealed.
One of the crimes Regan is accused off is supplying Iraq with information to help them shoot down an American or British jet patrolling over the no fly zone. This seems to be the act that prosecutors are basing their decision to charg him with capital espionage as it fits one of the criteria of the new legislation.