Seattle City Attorney Pete Holmes on Friday apologized for violating workplace rules by bringing bags of marijuana he purchased from newly-opened Washington state pot shops back to his office.

Holmes was one of the first people in line earlier this week as the first few marijuana retail shops opened across Washington state, where voters in 2012 sanctioned the sale of cannabis to adults for recreational use under a steeply taxed and regulated system.

"When I brought the unopened marijuana to City offices - trying to keep up with a busy schedule - I nonetheless violated the City's rules," Holmes said in a statement on the city's website.

"At the end of the business day, I took the marijuana home and left it there, still unopened, before I participated in the second Community Walk of the Mayor's Summer of Safety."

Holmes on Friday apologized, volunteered to donate $3,000 to a downtown homeless shelter, and voiced his on-going support for the state's landmark initiative.

On Tuesday, a suit-and-tie clad Holmes could be seen holding up a brown paper bag carrying marijuana he bought minutes before at Seattle's first pot shop for a sea of journalists.

"The most important take away here is that today marijuana sales became legal and I'm here to personally exercise myself this new freedom," Holmes told media.

"I bought two two-gram bags of OG Pearl, which was recommended. I'm keeping one bag for posterity and one for personal enjoyment at some point when it's appropriate," said Holmes, who was elected in 2009.

The drugs-at-work violation reflects a thorny reality for users in Washington state in that marijuana is still considered illegal by the U.S. government and Holmes said in his statement that Seattle is a "drug-free workplace" under federal law.

"Not only are controlled substances (like marijuana) banned from city offices, City employees cannot possess them while on City business," Holmes wrote on Friday.