"I think they still steal signs, and we'll have to keep an eye on that," Leach said. "That is a very unsavory practice they have, so we'll have to do what we can to defend against it."
Leach made similar comments last year about the Sun Devils' attempts to steal signs -- a practice that is not prohibited -- and said the conference should launch an investigation.
"Conference rules prohibit Pac-12 member institutions from disparaging each other and discrediting other institutions," Pac-12 commissioner Larry Scott said in a statement. "Information or accusations relative to rule violations must be handled by institutions filing those concerns with the conference office through a formal process, and institutions must refrain from discussing those concerns publicly."
Leach declined comment Friday.
A Pac-12 spokesman told ESPN.com the money from the fines would be applied to a postgraduate scholarship fund.
Washington State (4-2, 3-0 Pac-12) travels to Arizona State (5-2, 2-2) on Saturday (7 p.m. PT, Pac-12 Network).
Arizona State athletic director Ray Anderson applauded the conference's decision.
"Our professional integrity was questioned for two straight years by Mike Leach's irresponsible comments and we will not allow that to happen," Anderson said in a statement. "We are pleased with the outcome and for us the matter is closed."
Leach said he had heard rumors about microphones and cameras.
"They have a whole command center," he said.
Scott noted in his statement there are no playing rules that restrict a team from observing an opponent's offensive or defensive signals.
"The NCAA playing rules (1-4-11-a, b and f) cover what audio and video equipment is prohibited in the team area, coaching box and coaches' booth, and specifically state that any attempt to record, either through audio or video means, any signals given by an opposing player, coach or other team personal is prohibited," Scott said.
Information from ESPN's Chantel Jennings, Kevin Gemmell and The Associated Press was used in this report.