Liberal MP for Charlottetown Sean Casey discovered the marijuana delivery when he re-opened his constituency office after the holidays. (CBC)

Charlottetown MP Sean Casey decided return to sender was the best option when he found a brown envelope of medical marijuana on his desk at his P.E.I. office recently.

One gram samples were mailed to all Liberal MPs by Dana Larsen, a founding member of the Marijuana Party. Larsen wanted to remind the MPs of their election promise to legalize pot.

Casey said when he returned to his office after the holidays it was clear what was in the envelope.

"The constituency office was closed between Christmas and New Year's, and my first day back in the office I walk into my office and I hit a wall of a pungent aroma," he said.

"I marched it back out to the front desk and asked my assistant to send it right back to him, and that's what's been done."

A day later, Casey got a directive from the Liberal Party of Canada that the package should be given to the RCMP.

Casey said his party is still committed to legalizing marijuana. The first step, he said, will be setting up a task force to help with the implementation.

Selling pot at liquor stores is one model being considered.

Casey said his personal stand on the issue is that Canada's current laws regarding marijuana are not working, and he has yet to hear a more effective plan than legalizing it.

He believes legalization will help keep marijuana out of the hands of young people, and free up police resources for better use.