California Treasurer Bill Lockyer has joined the Irvine office of Boston-based law firm Brown Rudnick LLP on a part-time basis.

Lockyer will serve in the firm’s government law and strategies group, and is expected to remain in his role as treasurer until his term ends in January, 2015.

The state’s constitution prohibits state officers from “knowingly [receiving] any salary, wages, commissions, or other similar earned income from a lobbyist or lobbying firm.” Brown Rudnick is not registered as a lobbying firm in California.

Ronald Rus, who heads Brown Rudnick’s Irvine office, said Lockyer “will become an integral part of our strategic plan to grow our Orange County office, and to diversify the depth and range of legal services offered to our clients.”

Lockyer, 72, has held various state elective offices since 1973, including a seat in the State Assembly and two terms as attorney general. He became state treasurer in 2007.

He has previously worked for Hayward-based Furtado Jaspovice & Simons LC while serving as state treasurer.

Lockyer is married to Nadia Lockyer, former Santa Ana Board of Education trustee and Alameda County supervisor.