U.S. Capitol Police arrested seven activists and confiscated about 1,000 joints from marijuana activists on Thursday during a 4/20 "celebration."

DCMJ, the Washington D.C.-based marijuana advocacy group that spearheaded the legalization of cannabis in the district, led its first annual Congressional #JointSession -- the group planned to pass out two joints per person to members of Congress, congressional staffers and anyone who obtained a congressional ID (and is over the age of 21) from noon until 4:20 p.m.

U.S. Capitol Police confirmed the arrests.

"Under federal law, it is unlawful to possess marijuana," U.S. Capitol Police said in a statement. "As of 2:30 p.m., one adult male and two adult female arrestees were charged with possession with intent to distribute. Four adult females were charged with possession. They were taken to USCP Headquarters for processing."

“We didn’t plan on getting arrested today -- we brought 1,227 joints to represent the cannabis reform bill H.R. 1227 -- and gave away a few hundred to congressional staffers before Capitol Police took it all away,” DCMJ Founder Nikolas Schiller told Fox News. “This was meant to be a free speech event and was meant to influence members of Congress.”

For cannibas aficionados, ‘Weed Day’ is April 20, shortened to 4/20 -- a code-term for marijuana coined, according to several
reports, in 1971 by a group of California high school students who would meet at 4:20 p.m. every day after class to smoke pot.

The #JointSession event, according to DCMJ, was an effort to lobby members of Congress to encourage House Speaker Paul Ryan, R-Wis., to reauthorize the Rohrabacher-Farr amendment which prohibits the Department of Justice and the Drug Enforcement Administration from using funds to "interfere" with D.C. and state medical cannabis laws. The amendment expires on April 28.

Schiller told Fox News that DCMJ set up its demonstration on non-federal land near the Capitol.

“We were on D.C. grounds, but Capitol Police invoked federal law,” Schiller said. “We intend on fighting the charges.”

DCMJ had scheduled a “smoke-in” on the Capitol steps on April 24, but Schiller told Fox News he was unsure whether that event would take place as planned.

“Monday’s event is up in the air,” Schiller said. “We will see.”

Fox News' Chad Pergram contributed to this report.